Comitê Gestor
IF-UFF
Pedro Paulo M. Venezuela
Publicações
2026
Barboza, Elisangela Silva; Dias, Alexandre C.; Costa, Diego R.; Farias, Gil Aquino; Venezuela, Pedro; Lima, Erika N.; Pereira, Teldo A. S.
First-principles investigation of 2D honeycomb III–V semiconductors: Stability, electronic structure, excitons and optical response Journal Article
Em: Computational Condensed Matter, vol. 48, 2026, ISSN: 2352-2143.
@article{daSilvaBarboza2026,
title = {First-principles investigation of 2D honeycomb III–V semiconductors: Stability, electronic structure, excitons and optical response},
author = {Elisangela Silva Barboza and Alexandre C. Dias and Diego R. Costa and Gil Aquino Farias and Pedro Venezuela and Erika N. Lima and Teldo A. S. Pereira},
doi = {10.1016/j.cocom.2026.e01351},
issn = {2352-2143},
year = {2026},
date = {2026-10-01},
journal = {Computational Condensed Matter},
volume = {48},
publisher = {Elsevier BV},
abstract = {This study investigates the structural, electronic, vibrational, optical, and excitonic properties of conventional III–V semiconductors organized in a two-dimensional honeycomb lattice. Our methodology integrates first-principles calculations based on Density Functional Theory (DFT), supplemented by ab initio molecular dynamics (AIMD) simulations up to 300 K to confirm thermal stability. The dynamic stability was further corroborated through rigorous phonon dispersion analysis. Furthermore, a tight-binding method based on maximally localized Wannier functions, combined with the resolution of the Bethe–Salpeter equation was employed to elucidate the electronic structure and the influence of excitonic effects on the linear optical response. These findings provide a comprehensive understanding of the fundamental physics of III–V semiconductors in 2D architectures, establishing the theoretical benchmarks for their potential performance in advanced optoelectronic applications.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
This study investigates the structural, electronic, vibrational, optical, and excitonic properties of conventional III–V semiconductors organized in a two-dimensional honeycomb lattice. Our methodology integrates first-principles calculations based on Density Functional Theory (DFT), supplemented by ab initio molecular dynamics (AIMD) simulations up to 300 K to confirm thermal stability. The dynamic stability was further corroborated through rigorous phonon dispersion analysis. Furthermore, a tight-binding method based on maximally localized Wannier functions, combined with the resolution of the Bethe–Salpeter equation was employed to elucidate the electronic structure and the influence of excitonic effects on the linear optical response. These findings provide a comprehensive understanding of the fundamental physics of III–V semiconductors in 2D architectures, establishing the theoretical benchmarks for their potential performance in advanced optoelectronic applications.
Oliveira, P. R. A.; Codeço, C.; Menezes, M. G.; Venezuela, P.; Stavale, F.; Boscoboinik, J. A.
Co-adsorption mechanism drives CO oxidation on defective ZnS Miscellaneous
2026.
@misc{deoliveira2026coadsorptionmechanismdrivesoxidation,
title = {Co-adsorption mechanism drives CO oxidation on defective ZnS},
author = {P. R. A. Oliveira and C. Codeço and M. G. Menezes and P. Venezuela and F. Stavale and J. A. Boscoboinik},
url = {https://arxiv.org/abs/2606.00264},
year = {2026},
date = {2026-05-29},
urldate = {2026-05-29},
abstract = {Reactivity on wide-bandgap semiconductor surfaces relies critically on the generation of active sites. In the case of CO oxidation, however, the mere presence of defects is insufficient to drive reactivity. Here, we investigate CO oxidation on a defective ZnS single-crystal surface by combining near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) and density functional theory (DFT) calculations. NAP-XPS measurements reveal CO-like surface intermediates only under oxygen-rich conditions, consistent with oxygen-assisted CO oxidation. DFT calculations support an oxygen-assisted co-adsorption pathway in which CO interacts preferentially with adsorbed oxygen species stabilized near Zn-deficient sites, forming weakly bound CO-like structures. These results identify oxygen coverage, rather than defect density alone, as the key factor controlling CO-like intermediate formation on defective ZnS and establish defective ZnS as a model platform for studying oxygen-assisted surface chemistry on non-oxide semiconductors.},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Reactivity on wide-bandgap semiconductor surfaces relies critically on the generation of active sites. In the case of CO oxidation, however, the mere presence of defects is insufficient to drive reactivity. Here, we investigate CO oxidation on a defective ZnS single-crystal surface by combining near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) and density functional theory (DFT) calculations. NAP-XPS measurements reveal CO-like surface intermediates only under oxygen-rich conditions, consistent with oxygen-assisted CO oxidation. DFT calculations support an oxygen-assisted co-adsorption pathway in which CO interacts preferentially with adsorbed oxygen species stabilized near Zn-deficient sites, forming weakly bound CO-like structures. These results identify oxygen coverage, rather than defect density alone, as the key factor controlling CO-like intermediate formation on defective ZnS and establish defective ZnS as a model platform for studying oxygen-assisted surface chemistry on non-oxide semiconductors.
Torres, Vanessa; Albuquerque, Marcelo; Vivas, Richard Javier Caraballo; COSTA, LUCIANO T. T; Venezuela, Pedro
Interfacial properties of imidazolium-based ionic liquids on MAPbI _3 perovskite: a molecular dynamics study Journal Article
Em: J. Phys. D: Appl. Phys., 2026, ISSN: 1361-6463.
@article{Torres2026,
title = {Interfacial properties of imidazolium-based ionic liquids on MAPbI _3 perovskite: a molecular dynamics study},
author = {Vanessa Torres and Marcelo Albuquerque and Richard Javier Caraballo Vivas and LUCIANO T. T COSTA and Pedro Venezuela},
doi = {10.1088/1361-6463/ae6b9c},
issn = {1361-6463},
year = {2026},
date = {2026-05-11},
urldate = {2026-05-11},
journal = {J. Phys. D: Appl. Phys.},
publisher = {IOP Publishing},
abstract = {<jats:title>Abstract</jats:title>
<jats:p>
The performance and stability of perovskite solar cells (PSCs) are strongly influenced by interfacial properties, particularly at the charge transport layers, where surface defects can affect efficiency. The interaction between ionic liquids (ILs) and metal halide perovskites has attracted increasing attention due to their potential to enhance device performance and stability. In this study, we employ molecular dynamics simulations to investigate the interfacial behavior of imidazolium-based ILs on the defect-free (001) PbI
<jats:sub>2</jats:sub>
-flat surface of methylammonium lead iodide perovskite (MAPbI
<jats:sub>3</jats:sub>
), focusing on their structural, dynamic, and electrostatic properties.
Our results reveal the formation of a well-defined ionic layer near the perovskite surface, where the structural organization is strongly influenced by ion size, with larger anions promoting a more ordered arrangement. Dynamical analysis shows that ion mobility is significantly reduced in the interfacial region, correlating with the presence of an organized anionic layer. Additionally, dipole moment analysis indicates a predominant orientation along the surface normal, with notable fluctuations reflecting charge redistribution and molecular reorientation. Based on radial dipole distribution, we determined that the anion type significantly affects the dipolar correlation in the system. These results highlight the intricate relationship between the structural organization of IL constituents, ion-specific interactions, and dynamic behavior at the perovskite-IL interface, providing key insights into the role of ILs in interfacial design for enhancing PSC stability and performance.
</jats:p>},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
<jats:title>Abstract</jats:title>
<jats:p>
The performance and stability of perovskite solar cells (PSCs) are strongly influenced by interfacial properties, particularly at the charge transport layers, where surface defects can affect efficiency. The interaction between ionic liquids (ILs) and metal halide perovskites has attracted increasing attention due to their potential to enhance device performance and stability. In this study, we employ molecular dynamics simulations to investigate the interfacial behavior of imidazolium-based ILs on the defect-free (001) PbI
<jats:sub>2</jats:sub>
-flat surface of methylammonium lead iodide perovskite (MAPbI
<jats:sub>3</jats:sub>
), focusing on their structural, dynamic, and electrostatic properties.
Our results reveal the formation of a well-defined ionic layer near the perovskite surface, where the structural organization is strongly influenced by ion size, with larger anions promoting a more ordered arrangement. Dynamical analysis shows that ion mobility is significantly reduced in the interfacial region, correlating with the presence of an organized anionic layer. Additionally, dipole moment analysis indicates a predominant orientation along the surface normal, with notable fluctuations reflecting charge redistribution and molecular reorientation. Based on radial dipole distribution, we determined that the anion type significantly affects the dipolar correlation in the system. These results highlight the intricate relationship between the structural organization of IL constituents, ion-specific interactions, and dynamic behavior at the perovskite-IL interface, providing key insights into the role of ILs in interfacial design for enhancing PSC stability and performance.
</jats:p>
<jats:p>
The performance and stability of perovskite solar cells (PSCs) are strongly influenced by interfacial properties, particularly at the charge transport layers, where surface defects can affect efficiency. The interaction between ionic liquids (ILs) and metal halide perovskites has attracted increasing attention due to their potential to enhance device performance and stability. In this study, we employ molecular dynamics simulations to investigate the interfacial behavior of imidazolium-based ILs on the defect-free (001) PbI
<jats:sub>2</jats:sub>
-flat surface of methylammonium lead iodide perovskite (MAPbI
<jats:sub>3</jats:sub>
), focusing on their structural, dynamic, and electrostatic properties.
Our results reveal the formation of a well-defined ionic layer near the perovskite surface, where the structural organization is strongly influenced by ion size, with larger anions promoting a more ordered arrangement. Dynamical analysis shows that ion mobility is significantly reduced in the interfacial region, correlating with the presence of an organized anionic layer. Additionally, dipole moment analysis indicates a predominant orientation along the surface normal, with notable fluctuations reflecting charge redistribution and molecular reorientation. Based on radial dipole distribution, we determined that the anion type significantly affects the dipolar correlation in the system. These results highlight the intricate relationship between the structural organization of IL constituents, ion-specific interactions, and dynamic behavior at the perovskite-IL interface, providing key insights into the role of ILs in interfacial design for enhancing PSC stability and performance.
</jats:p>
Venezuela, Pedro; Marinho, Enesio; Rocha, Alexandre Reily; Villegas, Cesar E. P.
Layer-Dependent Optical Properties of Orthorhombic B _2 N _2 : Prospects for Photovoltaics Journal Article
Em: ACS Appl. Energy Mater., 2026, ISSN: 2574-0962.
@article{Venezuela2026,
title = {Layer-Dependent Optical Properties of Orthorhombic B _2 N _2 : Prospects for Photovoltaics},
author = {Pedro Venezuela and Enesio Marinho and Alexandre Reily Rocha and Cesar E. P. Villegas},
doi = {10.1021/acsaem.6c00153},
issn = {2574-0962},
year = {2026},
date = {2026-04-16},
urldate = {2026-04-16},
journal = {ACS Appl. Energy Mater.},
publisher = {American Chemical Society (ACS)},
abstract = {Fundamental understanding of exciton formation is of utmost importance for a wide variety of optoelectronic applications, as this elementary quasiparticle strongly influences the absorption, charge separation, and photocurrent generation processes. While hexagonal boron nitride stands out for its high thermal stability and chemical inertness, its wide band gap hampers its use in several optoelectronic applications, including photovoltaics. Here, by employing ab initio many-body excited-state methods, we elucidate how the electronic and optical properties of orthorhombic B2N2 evolve with layer thickness, from the three-dimensional bulk to intermediate multilayers and down to the monolayer limit. The results indicate that the quasiparticle gap can be tuned from 2.41 eV, for the monolayer, down to 1.28 eV in the bulk limit. Interestingly, the studied excitonic response exhibits prominent peaks in the near-infrared range, going from 1.4 to 1.7 eV, which highlights their potential as an active sunlight absorber material. Finally, we model a prototypical single-junction solar cell based on bulk B2N2, finding that a 150-nm-thick active layer achieves power conversion efficiencies between 16.8% and 24.9% in the nonradiative and radiative limits, respectively. Our calculations suggest the potential of B2N2-based thin films for the design of flexible solar cells.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Fundamental understanding of exciton formation is of utmost importance for a wide variety of optoelectronic applications, as this elementary quasiparticle strongly influences the absorption, charge separation, and photocurrent generation processes. While hexagonal boron nitride stands out for its high thermal stability and chemical inertness, its wide band gap hampers its use in several optoelectronic applications, including photovoltaics. Here, by employing ab initio many-body excited-state methods, we elucidate how the electronic and optical properties of orthorhombic B2N2 evolve with layer thickness, from the three-dimensional bulk to intermediate multilayers and down to the monolayer limit. The results indicate that the quasiparticle gap can be tuned from 2.41 eV, for the monolayer, down to 1.28 eV in the bulk limit. Interestingly, the studied excitonic response exhibits prominent peaks in the near-infrared range, going from 1.4 to 1.7 eV, which highlights their potential as an active sunlight absorber material. Finally, we model a prototypical single-junction solar cell based on bulk B2N2, finding that a 150-nm-thick active layer achieves power conversion efficiencies between 16.8% and 24.9% in the nonradiative and radiative limits, respectively. Our calculations suggest the potential of B2N2-based thin films for the design of flexible solar cells.
Venezuela, Pedro; Marinho, Enesio; Rocha, Alexandre Reily; Villegas, Cesar E. P.
Layer-Dependent Optical Properties of Orthorhombic B _2 N _2 : Prospects for Photovoltaics Journal Article
Em: ACS Appl. Energy Mater., 2026, ISSN: 2574-0962.
@article{Venezuela2026b,
title = {Layer-Dependent Optical Properties of Orthorhombic B _2 N _2 : Prospects for Photovoltaics},
author = {Pedro Venezuela and Enesio Marinho and Alexandre Reily Rocha and Cesar E. P. Villegas},
doi = {10.1021/acsaem.6c00153},
issn = {2574-0962},
year = {2026},
date = {2026-04-16},
urldate = {2026-04-16},
journal = {ACS Appl. Energy Mater.},
publisher = {American Chemical Society (ACS)},
abstract = {Fundamental understanding of exciton formation is of utmost importance for a wide variety of optoelectronic applications, as this elementary quasiparticle strongly influences the absorption, charge separation, and photocurrent generation processes. While hexagonal boron nitride stands out for its high thermal stability and chemical inertness, its wide band gap hampers its use in several optoelectronic applications, including photovoltaics. Here, by employing ab initio many-body excited-state methods, we elucidate how the electronic and optical properties of orthorhombic B2N2 evolve with layer thickness, from the three-dimensional bulk to intermediate multilayers and down to the monolayer limit. The results indicate that the quasiparticle gap can be tuned from 2.41 eV, for the monolayer, down to 1.28 eV in the bulk limit. Interestingly, the studied excitonic response exhibits prominent peaks in the near-infrared range, going from 1.4 to 1.7 eV, which highlights their potential as an active sunlight absorber material. Finally, we model a prototypical single-junction solar cell based on bulk B2N2, finding that a 150-nm-thick active layer achieves power conversion efficiencies between 16.8% and 24.9% in the nonradiative and radiative limits, respectively. Our calculations suggest the potential of B2N2-based thin films for the design of flexible solar cells.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Fundamental understanding of exciton formation is of utmost importance for a wide variety of optoelectronic applications, as this elementary quasiparticle strongly influences the absorption, charge separation, and photocurrent generation processes. While hexagonal boron nitride stands out for its high thermal stability and chemical inertness, its wide band gap hampers its use in several optoelectronic applications, including photovoltaics. Here, by employing ab initio many-body excited-state methods, we elucidate how the electronic and optical properties of orthorhombic B2N2 evolve with layer thickness, from the three-dimensional bulk to intermediate multilayers and down to the monolayer limit. The results indicate that the quasiparticle gap can be tuned from 2.41 eV, for the monolayer, down to 1.28 eV in the bulk limit. Interestingly, the studied excitonic response exhibits prominent peaks in the near-infrared range, going from 1.4 to 1.7 eV, which highlights their potential as an active sunlight absorber material. Finally, we model a prototypical single-junction solar cell based on bulk B2N2, finding that a 150-nm-thick active layer achieves power conversion efficiencies between 16.8% and 24.9% in the nonradiative and radiative limits, respectively. Our calculations suggest the potential of B2N2-based thin films for the design of flexible solar cells.
Oliveira, P. R. A; Venezuela, P.; Stavale, F.; Boscoboinik, J. A.
Insights into $CO_2$ activation on defective ZnS surfaces Miscellaneous
2026.
@misc{deoliveira2026insightsco2activationdefective,
title = {Insights into $CO_2$ activation on defective ZnS surfaces},
author = {P. R. A Oliveira and P. Venezuela and F. Stavale and J. A. Boscoboinik},
url = {https://arxiv.org/abs/2601.13434},
year = {2026},
date = {2026-01-19},
urldate = {2026-01-01},
abstract = {In this work, we investigate activation on ZnS using Near Ambient-Pressure X-ray photoelectron spectroscopy measurements (NAP-XPS) and density functional theory calculations (DFT). Our NAP-XPS experiments reveal that adsorbs onto a defective ZnS surface upon heating above in a atmosphere (up to ). The adsorption fingerprint is detectable even after cooling to room temperature under ultra-high vacuum. Our DFT calculations suggest that adsorption is energetically favorable on ZnS surfaces containing zinc vacancies, highlighting defect sites as key adsorption centers. Additionally, oxygen adsorption on a defective ZnS surface is exothermic, in contrast to the endothermic behavior observed on a defect-free surface. These findings contribute to a deeper understanding of defect-driven surface reactivity and may inform ZnS-based catalyst's design for capture and reutilization.},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
In this work, we investigate activation on ZnS using Near Ambient-Pressure X-ray photoelectron spectroscopy measurements (NAP-XPS) and density functional theory calculations (DFT). Our NAP-XPS experiments reveal that adsorbs onto a defective ZnS surface upon heating above in a atmosphere (up to ). The adsorption fingerprint is detectable even after cooling to room temperature under ultra-high vacuum. Our DFT calculations suggest that adsorption is energetically favorable on ZnS surfaces containing zinc vacancies, highlighting defect sites as key adsorption centers. Additionally, oxygen adsorption on a defective ZnS surface is exothermic, in contrast to the endothermic behavior observed on a defect-free surface. These findings contribute to a deeper understanding of defect-driven surface reactivity and may inform ZnS-based catalyst's design for capture and reutilization.
Lizárraga, K.; Villegas, Cesar E. P.; Lira, R.; Serquen, E.; Liu, Hsiang-Lin; Guerra, J. A.; Rocha, A. R.; Venezuela, P.
Dispersion model for the optical absorption of two-dimensional materials Journal Article
Em: Phys. Rev. B, vol. 113, não 4, 2026, ISSN: 2469-9969.
@article{Lizárraga2026,
title = {Dispersion model for the optical absorption of two-dimensional materials},
author = {K. Lizárraga and Cesar E. P. Villegas and R. Lira and E. Serquen and Hsiang-Lin Liu and J. A. Guerra and A. R. Rocha and P. Venezuela},
doi = {10.1103/2mhl-4vgh},
issn = {2469-9969},
year = {2026},
date = {2026-01-07},
journal = {Phys. Rev. B},
volume = {113},
number = {4},
publisher = {American Physical Society (APS)},
abstract = {The optical response of two-dimensional systems is strongly influenced by tightly bound excitons. Despite its relevance in helping predict device performance, the current derivation of the two-dimensional Elliott equation is rarely used to estimate exciton binding energy and band gap in these systems, primarily due to its lack of an analytical form and the complexity introduced by substrate interactions. In this work, we present a new approach based on optical absorption measurements via an extended Elliott band fluctuations model, which notably provides analytical expressions for isotropic systems. Our method accurately captures the optical absorption near the band edge, fully incorporating spin–orbit band splitting and substrate effects via the Keldysh effective potential. It also includes the influence of surface and interface contributions to the dielectric environment, which give rise to localized defect-related absorption features. We apply this approach to key transition metal dichalcogenides (MoS2, MoSe2, WS2, and WSe2) exhibiting small and large spin-orbit band splitting, on various substrates and over a broad temperature range. The results show good agreement with magnetoabsorption and photoluminescence measurements, allowing for an accurate description of excitonic properties using only optical measurements and is readily extendable to other 2D isotropic materials.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The optical response of two-dimensional systems is strongly influenced by tightly bound excitons. Despite its relevance in helping predict device performance, the current derivation of the two-dimensional Elliott equation is rarely used to estimate exciton binding energy and band gap in these systems, primarily due to its lack of an analytical form and the complexity introduced by substrate interactions. In this work, we present a new approach based on optical absorption measurements via an extended Elliott band fluctuations model, which notably provides analytical expressions for isotropic systems. Our method accurately captures the optical absorption near the band edge, fully incorporating spin–orbit band splitting and substrate effects via the Keldysh effective potential. It also includes the influence of surface and interface contributions to the dielectric environment, which give rise to localized defect-related absorption features. We apply this approach to key transition metal dichalcogenides (MoS2, MoSe2, WS2, and WSe2) exhibiting small and large spin-orbit band splitting, on various substrates and over a broad temperature range. The results show good agreement with magnetoabsorption and photoluminescence measurements, allowing for an accurate description of excitonic properties using only optical measurements and is readily extendable to other 2D isotropic materials.
Rivera, Daniel; Venezuela, Pedro; Lima, Luis H.; Champi, Ana; Barreto, Lucas
DFT+U: a Hubbard Hamiltonian-based correction for modeling localized electronic states Journal Article
Em: Rev. Bras. Ensino Fís., vol. 48, 2026, ISSN: 1806-9126.
@article{Rivera2026,
title = {DFT+U: a Hubbard Hamiltonian-based correction for modeling localized electronic states},
author = {Daniel Rivera and Pedro Venezuela and Luis H. Lima and Ana Champi and Lucas Barreto},
doi = {10.1590/1806-9126-rbef-2025-0340},
issn = {1806-9126},
year = {2026},
date = {2026-01-01},
journal = {Rev. Bras. Ensino Fís.},
volume = {48},
publisher = {FapUNIFESP (SciELO)},
abstract = {<jats:p>Abstract Density Functional Theory (DFT) is a widely used method to calculate the electronic structure of materials. One of the pivotal ingredients in the traditional DFT modeling strategy is the Exchange and Correlation Functional ( E X C). An inappropriate choice of the E X C can lead to substantially erroneous predictions. For example, the Generalized Gradient Approximation (GGA) dramatically fails to predict the band gap of strongly correlated systems. DFT + U, a corrective methodology based on the Hubbard model, offers a cost-effective approach to address this problem. This work provides an introductory overview of the DFT + U method. First, we discuss the importance of the E X C functional in DFT, and then we introduce the DFT+U approach. Subsequently, we illustrate the method’s applicability by calculating the electronic, magnetic, and structural properties of FeO using PBE and PBE+U functionals. We show that GGA fails to describe the electronic character and magnetic ordering of FeO, while DFT + U provides an accurate description of the FeO properties.</jats:p>},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
<jats:p>Abstract Density Functional Theory (DFT) is a widely used method to calculate the electronic structure of materials. One of the pivotal ingredients in the traditional DFT modeling strategy is the Exchange and Correlation Functional ( E X C). An inappropriate choice of the E X C can lead to substantially erroneous predictions. For example, the Generalized Gradient Approximation (GGA) dramatically fails to predict the band gap of strongly correlated systems. DFT + U, a corrective methodology based on the Hubbard model, offers a cost-effective approach to address this problem. This work provides an introductory overview of the DFT + U method. First, we discuss the importance of the E X C functional in DFT, and then we introduce the DFT+U approach. Subsequently, we illustrate the method’s applicability by calculating the electronic, magnetic, and structural properties of FeO using PBE and PBE+U functionals. We show that GGA fails to describe the electronic character and magnetic ordering of FeO, while DFT + U provides an accurate description of the FeO properties.</jats:p>
Rivera, Daniel; Venezuela, Pedro; Lima, Luis H.; Champi, Ana; Barreto, Lucas
DFT+U: a Hubbard Hamiltonian-based correction for modeling localized electronic states Journal Article
Em: Rev. Bras. Ensino Fís., vol. 48, 2026, ISSN: 1806-9126.
@article{Rivera2026b,
title = {DFT+U: a Hubbard Hamiltonian-based correction for modeling localized electronic states},
author = {Daniel Rivera and Pedro Venezuela and Luis H. Lima and Ana Champi and Lucas Barreto},
doi = {10.1590/1806-9126-rbef-2025-0340},
issn = {1806-9126},
year = {2026},
date = {2026-01-01},
journal = {Rev. Bras. Ensino Fís.},
volume = {48},
publisher = {FapUNIFESP (SciELO)},
abstract = {<jats:p>Abstract Density Functional Theory (DFT) is a widely used method to calculate the electronic structure of materials. One of the pivotal ingredients in the traditional DFT modeling strategy is the Exchange and Correlation Functional ( E X C). An inappropriate choice of the E X C can lead to substantially erroneous predictions. For example, the Generalized Gradient Approximation (GGA) dramatically fails to predict the band gap of strongly correlated systems. DFT + U, a corrective methodology based on the Hubbard model, offers a cost-effective approach to address this problem. This work provides an introductory overview of the DFT + U method. First, we discuss the importance of the E X C functional in DFT, and then we introduce the DFT+U approach. Subsequently, we illustrate the method’s applicability by calculating the electronic, magnetic, and structural properties of FeO using PBE and PBE+U functionals. We show that GGA fails to describe the electronic character and magnetic ordering of FeO, while DFT + U provides an accurate description of the FeO properties.</jats:p>},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
<jats:p>Abstract Density Functional Theory (DFT) is a widely used method to calculate the electronic structure of materials. One of the pivotal ingredients in the traditional DFT modeling strategy is the Exchange and Correlation Functional ( E X C). An inappropriate choice of the E X C can lead to substantially erroneous predictions. For example, the Generalized Gradient Approximation (GGA) dramatically fails to predict the band gap of strongly correlated systems. DFT + U, a corrective methodology based on the Hubbard model, offers a cost-effective approach to address this problem. This work provides an introductory overview of the DFT + U method. First, we discuss the importance of the E X C functional in DFT, and then we introduce the DFT+U approach. Subsequently, we illustrate the method’s applicability by calculating the electronic, magnetic, and structural properties of FeO using PBE and PBE+U functionals. We show that GGA fails to describe the electronic character and magnetic ordering of FeO, while DFT + U provides an accurate description of the FeO properties.</jats:p>
2025
Oliveira, P. R. A.; Coelho, I.; Felix, G.; Venezuela, P.; Stavale, F.
Growth and Surface Characterization of a Type-II ZnO/ZnS Heterostructure Journal Article
Em: J. Phys. Chem. C, 2025, ISSN: 1932-7455.
@article{deOliveira2025,
title = {Growth and Surface Characterization of a Type-II ZnO/ZnS Heterostructure},
author = {P. R. A. Oliveira and I. Coelho and G. Felix and P. Venezuela and F. Stavale},
doi = {10.1021/acs.jpcc.5c05124},
issn = {1932-7455},
year = {2025},
date = {2025-10-09},
urldate = {2025-10-09},
journal = {J. Phys. Chem. C},
publisher = {American Chemical Society (ACS)},
abstract = {We report the in situ formation of a type-II ZnO/ZnS heterostructure via the thermal oxidation of a ZnS(001) single crystal under a clean controlled oxygen atmosphere. By combining X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), we investigated the chemical composition, electronic structure, and surface morphology of the resulting interface. Core-level shifts observed in our XPS measurements suggest an upward band-bending due to the formation of a hybrid interface. AFM measurements show that ZnO grows through a layer-plus-island mode, forming distorted hexagonal nanoislands. Our band alignment analysis confirms the type-II heterostructure arrangement with suitable electronic band-edge positions for efficient charge separation, highlighting its potential as a platform for photocatalytic applications, such as hydrogen and oxygen evolution reactions (HER and OER).},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We report the in situ formation of a type-II ZnO/ZnS heterostructure via the thermal oxidation of a ZnS(001) single crystal under a clean controlled oxygen atmosphere. By combining X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), we investigated the chemical composition, electronic structure, and surface morphology of the resulting interface. Core-level shifts observed in our XPS measurements suggest an upward band-bending due to the formation of a hybrid interface. AFM measurements show that ZnO grows through a layer-plus-island mode, forming distorted hexagonal nanoislands. Our band alignment analysis confirms the type-II heterostructure arrangement with suitable electronic band-edge positions for efficient charge separation, highlighting its potential as a platform for photocatalytic applications, such as hydrogen and oxygen evolution reactions (HER and OER).
Caraballo-Vivas, Richard Javier; Albuquerque, Marcelo; Torres, Vanessa; Costa, Luciano T.; Venezuela, Pedro; Reis, Mario
Evidence of the Giant Barocaloric Effect in the PVA-Slime System by Molecular Dynamics Simulations Journal Article
Em: ACS Omega, 2025, ISSN: 2470-1343.
@article{Caraballo-Vivas2025,
title = {Evidence of the Giant Barocaloric Effect in the PVA-Slime System by Molecular Dynamics Simulations},
author = {Richard Javier Caraballo-Vivas and Marcelo Albuquerque and Vanessa Torres and Luciano T. Costa and Pedro Venezuela and Mario Reis},
doi = {10.1021/acsomega.5c02475},
issn = {2470-1343},
year = {2025},
date = {2025-08-23},
urldate = {2025-08-23},
journal = {ACS Omega},
publisher = {American Chemical Society (ACS)},
abstract = {Advancements in the study of the barocaloric effect in polymers have opened promising applications in both the scientific and industrial fields. Among these, elastic polymers based on poly(vinyl alcohol) (PVA), such as slimes, have shown significant potential for solid-state refrigeration and thermal battery applications due to their notable pressure-induced thermal response, which occurs without an associated structural phase transition. Thus, current research focuses on understanding the mechanism behind this response to applied pressure with the aim of optimizing its thermal performance. Therefore, we employed a molecular dynamics simulation in order to explore the barocaloric effect in the Slime system. We used pure PVA chains cross-linked by tetrahydroxyborate ions to provide further details about our Slime system, promoting a greater proximity between polymeric chains. Our results reveal that these connections reduce the free volume in the Slime system compared to pure PVA. This, combined with the applied simulated pressure, decreases the mobility of the polymer chains, lowering their kinetic energy while favoring potential energy. As a result, this contributes significantly to the change in internal energy and, consequently, to the barocaloric effect. Thus, our investigation shows a significant increase in entropy from 56 JK–1 kg–1 for pure PVA to 295 JK–1 kg–1 Slime system and temperature change from 3 to 26 K at 300 MPa. These findings highlight the importance of cross-linking between polymer chains, which enhances the barocaloric effect in this system type, offering promising prospects for practical applications.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Advancements in the study of the barocaloric effect in polymers have opened promising applications in both the scientific and industrial fields. Among these, elastic polymers based on poly(vinyl alcohol) (PVA), such as slimes, have shown significant potential for solid-state refrigeration and thermal battery applications due to their notable pressure-induced thermal response, which occurs without an associated structural phase transition. Thus, current research focuses on understanding the mechanism behind this response to applied pressure with the aim of optimizing its thermal performance. Therefore, we employed a molecular dynamics simulation in order to explore the barocaloric effect in the Slime system. We used pure PVA chains cross-linked by tetrahydroxyborate ions to provide further details about our Slime system, promoting a greater proximity between polymeric chains. Our results reveal that these connections reduce the free volume in the Slime system compared to pure PVA. This, combined with the applied simulated pressure, decreases the mobility of the polymer chains, lowering their kinetic energy while favoring potential energy. As a result, this contributes significantly to the change in internal energy and, consequently, to the barocaloric effect. Thus, our investigation shows a significant increase in entropy from 56 JK–1 kg–1 for pure PVA to 295 JK–1 kg–1 Slime system and temperature change from 3 to 26 K at 300 MPa. These findings highlight the importance of cross-linking between polymer chains, which enhances the barocaloric effect in this system type, offering promising prospects for practical applications.
Lizárraga, K.; Guerra, J. A.; Enrique-Moran, L. A.; Serquen, E.; Ventura, E.; Villegas, Cesar E. P.; Rocha, A. R.; Venezuela, P.
2025.
@misc{lizárraga2025determiningexcitonbindingenergy,
title = {Determining Exciton Binding Energy and Reduced Effective Mass in Metal Tri-Halide Perovskites from Optical and Impedance Spectroscopy Measurements},
author = {K. Lizárraga and J. A. Guerra and L. A. Enrique-Moran and E. Serquen and E. Ventura and Cesar E. P. Villegas and A. R. Rocha and P. Venezuela},
url = {https://arxiv.org/abs/2506.22680},
year = {2025},
date = {2025-06-27},
urldate = {2025-06-27},
abstract = {Accurate determination of the exciton binding energy and reduced effective mass in halide perovskites is of utmost importance for the selective design of optoelectronic devices. Although these properties are currently determined by several spectroscopic techniques, complementary theoretical models are often required to bridge macroscopic and microscopic properties. Here, we present a novel method to determine these quantities while fully accounting for polarization effects due to carrier interactions with longitudinal optical phonons. Our approach estimates the exciton-polaron binding energy from optical absorption measurements using a recently developed Elliott based Band Fluctuations model. The reduced effective mass is obtained via the Pollmann-Buttner exciton-polaron model, which is based on the Frohlich polaron framework, where the strength of the electron-phonon interaction arises from changes in the dielectric properties. The procedure is applied to the family of perovskites ABX3 (A = MA, FA, Cs; B = Pb; X = I, Br, Cl), showing excellent agreement with high field magnetoabsorption and other optical-resolved techniques. The results suggest that the Pollmann-Buttner model offers a robust and novel approach for determining the reduced effective mass in metal tri-halide perovskites and other polar materials exhibiting free exciton bands.},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Accurate determination of the exciton binding energy and reduced effective mass in halide perovskites is of utmost importance for the selective design of optoelectronic devices. Although these properties are currently determined by several spectroscopic techniques, complementary theoretical models are often required to bridge macroscopic and microscopic properties. Here, we present a novel method to determine these quantities while fully accounting for polarization effects due to carrier interactions with longitudinal optical phonons. Our approach estimates the exciton-polaron binding energy from optical absorption measurements using a recently developed Elliott based Band Fluctuations model. The reduced effective mass is obtained via the Pollmann-Buttner exciton-polaron model, which is based on the Frohlich polaron framework, where the strength of the electron-phonon interaction arises from changes in the dielectric properties. The procedure is applied to the family of perovskites ABX3 (A = MA, FA, Cs; B = Pb; X = I, Br, Cl), showing excellent agreement with high field magnetoabsorption and other optical-resolved techniques. The results suggest that the Pollmann-Buttner model offers a robust and novel approach for determining the reduced effective mass in metal tri-halide perovskites and other polar materials exhibiting free exciton bands.
Marinho, Enesio; Dias, Alexandre C.; Gomes, Lidia C.; Seridonio, Antonio C. F.; Meira, Gabriel M. C.; Souza, Mariano; Soares, Samuel M.; Squillante, Lucas; Venezuela, Pedro; Rocha, Alexandre R.; Villegas, Cesar E. P.
Optoelectronic properties of boron monochalcogenide monolayers: Quasiparticle and excitonic effects from first principles Journal Article
Em: Phys. Rev. B, vol. 111, não 23, 2025, ISSN: 2469-9969.
@article{Marinho2025,
title = {Optoelectronic properties of boron monochalcogenide monolayers: Quasiparticle and excitonic effects from first principles},
author = {Enesio Marinho and Alexandre C. Dias and Lidia C. Gomes and Antonio C. F. Seridonio and Gabriel M. C. Meira and Mariano Souza and Samuel M. Soares and Lucas Squillante and Pedro Venezuela and Alexandre R. Rocha and Cesar E. P. Villegas},
doi = {10.1103/v37y-njhk},
issn = {2469-9969},
year = {2025},
date = {2025-06-23},
journal = {Phys. Rev. B},
volume = {111},
number = {23},
publisher = {American Physical Society (APS)},
abstract = {We investigate the linear optical response and excitonic landscape in boron monochalcogenide (B𝑋, 𝑋 = S, Se, Te) single layers using ab initio many-body perturbation theory. These 2D monochalcogenides are wide band gap semiconductors, with the valence band exhibiting a quasiflat caldera-shaped dispersion in BS and BSe sheets, associated with strong van Hove singularities at the Fermi level in the density of states, an electronic feature that plays a crucial role in the emergence of strong excitonic effects. By solving the Bethe-Salpeter equation on top of 𝐺0𝑊0 quasiparticle energies, our results reveal that bound excitons arise from direct optical transitions between the highest occupied band and the lowest unoccupied band along the Γ−𝑀 and Γ−𝐾 paths. Additionally, in BS and BSe monolayers, we identify excitons that are bright for in-plane polarized incident light while becoming dark for out-of-plane polarization, and other excitons with the opposite behavior. The optical selection rules are described using group-theory analysis of wave-function symmetries, determining whether optical transitions are dipole allowed or forbidden. Furthermore, exciton radiative lifetimes are estimated to range from 0.2 ns to 1.6 ns at room temperature, while exciton binding energies are significantly high, ranging from 0.6 eV to 1.2 eV for both indirect ground-state excitons and zero-momentum direct excitons. Finally, the strong electron-hole interactions in these materials lead to the formation of tightly bound excitons with a small radius, paving the way for excitonic Bose-Einstein condensation in B𝑋 monolayers. Our study sheds light on the complex excitonic features of single-layer B𝑋, emphasizing its potential for cutting-edge applications in exciton-driven optoelectronics and quantum technologies.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We investigate the linear optical response and excitonic landscape in boron monochalcogenide (B𝑋, 𝑋 = S, Se, Te) single layers using ab initio many-body perturbation theory. These 2D monochalcogenides are wide band gap semiconductors, with the valence band exhibiting a quasiflat caldera-shaped dispersion in BS and BSe sheets, associated with strong van Hove singularities at the Fermi level in the density of states, an electronic feature that plays a crucial role in the emergence of strong excitonic effects. By solving the Bethe-Salpeter equation on top of 𝐺0𝑊0 quasiparticle energies, our results reveal that bound excitons arise from direct optical transitions between the highest occupied band and the lowest unoccupied band along the Γ−𝑀 and Γ−𝐾 paths. Additionally, in BS and BSe monolayers, we identify excitons that are bright for in-plane polarized incident light while becoming dark for out-of-plane polarization, and other excitons with the opposite behavior. The optical selection rules are described using group-theory analysis of wave-function symmetries, determining whether optical transitions are dipole allowed or forbidden. Furthermore, exciton radiative lifetimes are estimated to range from 0.2 ns to 1.6 ns at room temperature, while exciton binding energies are significantly high, ranging from 0.6 eV to 1.2 eV for both indirect ground-state excitons and zero-momentum direct excitons. Finally, the strong electron-hole interactions in these materials lead to the formation of tightly bound excitons with a small radius, paving the way for excitonic Bose-Einstein condensation in B𝑋 monolayers. Our study sheds light on the complex excitonic features of single-layer B𝑋, emphasizing its potential for cutting-edge applications in exciton-driven optoelectronics and quantum technologies.
Oliveira, P. R. A; Coelho, I.; Felix, G.; Venezuela, P.; Stavale, F.
In situ growth of a type-II ZnO/ZnS heterostructure:From stability to band-offset Miscellaneous
2025.
@misc{deoliveira2025situgrowthtypeiiznozns,
title = {In situ growth of a type-II ZnO/ZnS heterostructure:From stability to band-offset},
author = {P. R. A Oliveira and I. Coelho and G. Felix and P. Venezuela and F. Stavale},
url = {https://arxiv.org/abs/2506.14499},
year = {2025},
date = {2025-06-17},
urldate = {2025-01-01},
abstract = {We have successfully obtained a ZnO/ZnS heterostructure by heating a ZnS(001) single crystal in a controlled impurities-free oxygen atmosphere.
Combining X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM), we explore the stability, electronic structure, and morphology of that interface. Our XPS measurements reveal a binding energy shift of the core-level peaks, indicating a band-bending effect due to the formation of a hybrid ZnO/ZnS interface. In addition, AFM measurements show that exposure of ZnS single-crystal to an oxygen atmosphere leads to the formation of ZnO/ZnS-like islands. Interestingly, our band-offset estimation suggest a type-II heterostructure arrangement with suitable electronic edges positions that turn ZnO/ZnS heterostructure a promising platform for catalytic applications, particularly hydrogen and oxygen evolution reactions.},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
We have successfully obtained a ZnO/ZnS heterostructure by heating a ZnS(001) single crystal in a controlled impurities-free oxygen atmosphere.
Combining X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM), we explore the stability, electronic structure, and morphology of that interface. Our XPS measurements reveal a binding energy shift of the core-level peaks, indicating a band-bending effect due to the formation of a hybrid ZnO/ZnS interface. In addition, AFM measurements show that exposure of ZnS single-crystal to an oxygen atmosphere leads to the formation of ZnO/ZnS-like islands. Interestingly, our band-offset estimation suggest a type-II heterostructure arrangement with suitable electronic edges positions that turn ZnO/ZnS heterostructure a promising platform for catalytic applications, particularly hydrogen and oxygen evolution reactions.
Combining X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM), we explore the stability, electronic structure, and morphology of that interface. Our XPS measurements reveal a binding energy shift of the core-level peaks, indicating a band-bending effect due to the formation of a hybrid ZnO/ZnS interface. In addition, AFM measurements show that exposure of ZnS single-crystal to an oxygen atmosphere leads to the formation of ZnO/ZnS-like islands. Interestingly, our band-offset estimation suggest a type-II heterostructure arrangement with suitable electronic edges positions that turn ZnO/ZnS heterostructure a promising platform for catalytic applications, particularly hydrogen and oxygen evolution reactions.
Villegas, Cesar E. P.; Jr, Enesio Marinho; Dias, A. C.; Venezuela, Pedro; Rocha, Alexandre Reily
Optical properties of TiS3 as a novel thin film for single-junction and tandem solar cells Working paper
2025.
@workingpaper{villegas2025opticalpropertiestis3novel,
title = {Optical properties of TiS3 as a novel thin film for single-junction and tandem solar cells},
author = {Cesar E. P. Villegas and Enesio Marinho Jr and A. C. Dias and Pedro Venezuela and Alexandre Reily Rocha},
url = {https://arxiv.org/abs/2504.06368},
year = {2025},
date = {2025-04-08},
urldate = {2025-01-01},
abstract = {Sub-micrometer thin films are promising platforms for emerging flexible photovoltaic devices. Although the current market already produces efficient solar cells, the average wafer thickness of these devices remains far from the sub-micrometer scale, making them susceptible to cracking under bending stress and thus precluding their use in flexible device applications. Due to its earth abundance, non-toxicity, and low elastic modulus, titanium trisulfide (TiS3) has emerged as a promising alternative for flexible device applications. Here, using excited-state density functional calculations combined with the transfer matrix approach, we perform an optical analysis and assess the efficiency of a prototype photovoltaic device based on sub-micrometer TiS3 thin films. Using optical constants obtained from our first-principles calculations, we evaluate the photovoltaic response of a single-junction device in the radiative limit, finding that a 140-nm-thick active layer achieves a maximum power conversion efficiency of approximately 22%. Additionally, we investigate tandem solar cells that incorporate TiS3 into perovskite thin films, and find that the lower and upper power conversion efficiencies range from approximately 18% to 33%. Overall, our results suggest great potential for using TiS3 thin films as an active layer in the design of highly efficient flexible solar cells.},
keywords = {},
pubstate = {published},
tppubtype = {workingpaper}
}
Sub-micrometer thin films are promising platforms for emerging flexible photovoltaic devices. Although the current market already produces efficient solar cells, the average wafer thickness of these devices remains far from the sub-micrometer scale, making them susceptible to cracking under bending stress and thus precluding their use in flexible device applications. Due to its earth abundance, non-toxicity, and low elastic modulus, titanium trisulfide (TiS3) has emerged as a promising alternative for flexible device applications. Here, using excited-state density functional calculations combined with the transfer matrix approach, we perform an optical analysis and assess the efficiency of a prototype photovoltaic device based on sub-micrometer TiS3 thin films. Using optical constants obtained from our first-principles calculations, we evaluate the photovoltaic response of a single-junction device in the radiative limit, finding that a 140-nm-thick active layer achieves a maximum power conversion efficiency of approximately 22%. Additionally, we investigate tandem solar cells that incorporate TiS3 into perovskite thin films, and find that the lower and upper power conversion efficiencies range from approximately 18% to 33%. Overall, our results suggest great potential for using TiS3 thin films as an active layer in the design of highly efficient flexible solar cells.
Fujisawa, Kazunori; Carvalho, Bruno R.; Venezuela, Pedro; Kang, Cheon-Soo; Kim, Yoong Ahm; Hayashi, Takuya; Terrones, Mauricio
2025.
@workingpaper{fujisawa2025universalramanspectroscopicframework,
title = {A Universal Raman Spectroscopic Framework for Defect Quantification in Mono-to-Multilayer Graphenic Materials: The Graphene Atlas},
author = {Kazunori Fujisawa and Bruno R. Carvalho and Pedro Venezuela and Cheon-Soo Kang and Yoong Ahm Kim and Takuya Hayashi and Mauricio Terrones},
url = {https://arxiv.org/abs/2503.12459},
year = {2025},
date = {2025-03-16},
urldate = {2025-01-01},
abstract = {Point defects, though atomically small, significantly influence the properties of 2D materials. A general method for characterizing point defect density (nD) in graphenic materials with arbitrary layer number (nL) is currently lacking. Here, we introduce the Graphene Atlas, a non-destructive Raman spectroscopy-based framework for defect quantification in diverse graphenic systems. We demonstrate that the relative fractions of the double-resonance D and 2D Raman bands, which arise from competing scattering processes, exhibit a universal relationship with nD, independent of nL. Plotting Raman data on a plane defined by defect-related and layer number-related parameters enables a direct and quantitative determination of nD and nL. This Graphene Atlas provides a transformative tool for real-time defect quantification in scalable manufacturing of graphenic materials, bridging fundamental research and industrial applications. This framework establishes a new standard for defect characterization of graphenic systems, facilitating their optimization for advanced technological applications.},
keywords = {},
pubstate = {published},
tppubtype = {workingpaper}
}
Point defects, though atomically small, significantly influence the properties of 2D materials. A general method for characterizing point defect density (nD) in graphenic materials with arbitrary layer number (nL) is currently lacking. Here, we introduce the Graphene Atlas, a non-destructive Raman spectroscopy-based framework for defect quantification in diverse graphenic systems. We demonstrate that the relative fractions of the double-resonance D and 2D Raman bands, which arise from competing scattering processes, exhibit a universal relationship with nD, independent of nL. Plotting Raman data on a plane defined by defect-related and layer number-related parameters enables a direct and quantitative determination of nD and nL. This Graphene Atlas provides a transformative tool for real-time defect quantification in scalable manufacturing of graphenic materials, bridging fundamental research and industrial applications. This framework establishes a new standard for defect characterization of graphenic systems, facilitating their optimization for advanced technological applications.
Oliveira, P. R. A; Lima, L.; Felix, G.; Venezuela, Pedro; Stavale, F.
Formation mechanism, stability and role of zinc and sulfur vacancies on the electronic properties and optical response of ZnS Working paper
2025.
@workingpaper{deoliveira2025formationmechanismstabilityrole,
title = {Formation mechanism, stability and role of zinc and sulfur vacancies on the electronic properties and optical response of ZnS},
author = {P. R. A Oliveira and L. Lima and G. Felix and Pedro Venezuela and F. Stavale},
url = {https://arxiv.org/abs/2502.15670},
year = {2025},
date = {2025-02-21},
urldate = {2025-01-01},
abstract = {Combining experimental and theoretical tools, we report that Zn vacanciesplay an important role in the electronic and optical responses of ZnS sphalerite. The defective surface of ZnS (001) single crystal prepared in ultra-highvacuum conditions, has been shown to exhibit a semiconducting character instead of the insulating properties of the pristine structure, as revealed by X-ray photoelectron spectroscopy (XPS). Interestingly, this effect is attributed to the formation of zinc vacancies in the ZnS system, which also alter the optical response of the material, as supported by photoluminescence (PL) measurements comparing pristine and S-rich (Zn-poor) ZnS. To address these findings from a theoretical point of view, first principles calculations based on density functional theory (DFT) were performed. The optical properties of cation-defective ZnS were evaluated using random-phase approximation and hybrid functional DFT calculations. These calculations revealed absorption peaks in the visible range in the defective ZnS rather than solely in the ultra-violet range obtained for defect-free ZnS. The combination of this finding with joint density of states (JDOS) analysis explains the emergence of new luminescence peaks observed in the PL spectra of cation-defective ZnS. These findings highlight the role of Zn vacancies in tuning ZnS optical properties, making it a potential candidate for optoelectronic applications such as LEDs and photodetectors.},
keywords = {},
pubstate = {published},
tppubtype = {workingpaper}
}
Combining experimental and theoretical tools, we report that Zn vacanciesplay an important role in the electronic and optical responses of ZnS sphalerite. The defective surface of ZnS (001) single crystal prepared in ultra-highvacuum conditions, has been shown to exhibit a semiconducting character instead of the insulating properties of the pristine structure, as revealed by X-ray photoelectron spectroscopy (XPS). Interestingly, this effect is attributed to the formation of zinc vacancies in the ZnS system, which also alter the optical response of the material, as supported by photoluminescence (PL) measurements comparing pristine and S-rich (Zn-poor) ZnS. To address these findings from a theoretical point of view, first principles calculations based on density functional theory (DFT) were performed. The optical properties of cation-defective ZnS were evaluated using random-phase approximation and hybrid functional DFT calculations. These calculations revealed absorption peaks in the visible range in the defective ZnS rather than solely in the ultra-violet range obtained for defect-free ZnS. The combination of this finding with joint density of states (JDOS) analysis explains the emergence of new luminescence peaks observed in the PL spectra of cation-defective ZnS. These findings highlight the role of Zn vacancies in tuning ZnS optical properties, making it a potential candidate for optoelectronic applications such as LEDs and photodetectors.
Serquen, E.; Lizárraga, K.; Enrique, L. A.; Bravo, F.; Mishra, S.; LLontop, P.; Venezuela, Pedro; Tessler, L. R.; Guerra, J. A.
2025.
@workingpaper{serquen2025crystallineenvironmentluminescenttb3,
title = {On the crystalline environment of luminescent Tb3+ ions embedded in indium tin oxide thin films: a DFT and Crystal field analysis assessment},
author = {E. Serquen and K. Lizárraga and L. A. Enrique and F. Bravo and S. Mishra and P. LLontop and Pedro Venezuela and L. R. Tessler and J. A. Guerra},
url = {https://arxiv.org/abs/2502.08517},
doi = {https://doi.org/10.48550/arXiv.2502.08517},
year = {2025},
date = {2025-02-12},
urldate = {2025-02-12},
abstract = {We assess the local symmetry and crystal environment of trivalent terbium ions embedded in an indium tin oxide (ITO) matrix with bixbyite structure. The mboxTb3+ ions tend to substitute mboxIn3+ ions in two different cationic sites (b and d). Density Functional Theory (DFT) calculations suggest that the mboxTb3+ ions are mainly located at C2 symmetry sites relaxing selection rules and enabling electric dipole transitions, with the $^5textD_4rightarrowleftindex^7textF_2$ transition being the most intense, providing a red color to the light emission. Photoluminescence emission spectra under UV excitation at qty83kelvin revealed 30 intra-4f transitions, which were assigned to the $leftindex^7textF_J$ ground multiplet of the mboxTb3+ ion. Crystal-field analysis shows a strong alignment between calculated and observed energy levels, yielding a standard deviation of $sigma=qty15.1centipermetre$. We believe these results can help to understand the activation mechanisms of mboxTb3+ luminescent centers in transparent conductive oxides, as well as the potential to modulate mboxTb3+ emission color through its crystalline environment.},
keywords = {},
pubstate = {published},
tppubtype = {workingpaper}
}
We assess the local symmetry and crystal environment of trivalent terbium ions embedded in an indium tin oxide (ITO) matrix with bixbyite structure. The mboxTb3+ ions tend to substitute mboxIn3+ ions in two different cationic sites (b and d). Density Functional Theory (DFT) calculations suggest that the mboxTb3+ ions are mainly located at C2 symmetry sites relaxing selection rules and enabling electric dipole transitions, with the $^5textD_4rightarrowleftindex^7textF_2$ transition being the most intense, providing a red color to the light emission. Photoluminescence emission spectra under UV excitation at qty83kelvin revealed 30 intra-4f transitions, which were assigned to the $leftindex^7textF_J$ ground multiplet of the mboxTb3+ ion. Crystal-field analysis shows a strong alignment between calculated and observed energy levels, yielding a standard deviation of $sigma=qty15.1centipermetre$. We believe these results can help to understand the activation mechanisms of mboxTb3+ luminescent centers in transparent conductive oxides, as well as the potential to modulate mboxTb3+ emission color through its crystalline environment.
2024
Bertolini, Samuel; Delcorte, Arnaud; Venezuela, Pedro
Understanding the Self-Healing Electrostatic Shield Mechanism at the Lithium–Metal Anode Surface Journal Article
Em: Chem. Mater., 2024, ISSN: 1520-5002.
@article{Bertolini2024,
title = {Understanding the Self-Healing Electrostatic Shield Mechanism at the Lithium–Metal Anode Surface},
author = {Samuel Bertolini and Arnaud Delcorte and Pedro Venezuela},
url = {https://pubs.acs.org/doi/full/10.1021/acs.chemmater.4c01601},
doi = {10.1021/acs.chemmater.4c01601},
issn = {1520-5002},
year = {2024},
date = {2024-08-29},
urldate = {2024-08-29},
journal = {Chem. Mater.},
publisher = {American Chemical Society (ACS)},
abstract = {Lithium–metal anodes, with their impressive high specific capacity of approximately 3860 mAh/g, emerge as a promising alternative to Li-ion anodes. However, when subjected to higher recharge currents for accelerated battery charging, dendrites tend to form on the Li-metal surface. These dendrites can puncture the separator, leading to short circuits upon contact with the positive electrode. Such short circuits in a nonaqueous solvent can trigger runaway reactions, which raises safety concerns. In an effort to limit dendrite formation on the lithium–metal anode, the “self-healing” electrostatic shield mechanism (SHES) incorporates a small fraction of cesium salts in the electrolyte. These cesium ions remain charged on the surface, migrating toward the dendrites. The migration of Cs-ions to the dendrite surface creates a charged shield that compels lithium ions to deposit outside the dendrites, preventing the dendrite’s undesirable growth. To delve deeper into the working of the SHES mechanism, this study specifically utilizes Li and Cs atoms in both solvated and non-solvated configurations. These atoms are employed to be adsorbed onto various sites of the Li slab surface. Density functional theory (DFT) calculations are employed to explore the adsorption energy of Cs ions on Li-metal and their relationship with dendrite formation. In the presence of the solid electrolyte interphase (SEI), Cs ions migrate to damaged areas, depositing over the exposed bare metal surface and grain boundaries. When the SEI breaks, Cs ions cover the exposed Li surface, creating a positively charged shield in the exposed area, thereby reducing the pathway for Li plating and subsequent dendrite growth.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Lithium–metal anodes, with their impressive high specific capacity of approximately 3860 mAh/g, emerge as a promising alternative to Li-ion anodes. However, when subjected to higher recharge currents for accelerated battery charging, dendrites tend to form on the Li-metal surface. These dendrites can puncture the separator, leading to short circuits upon contact with the positive electrode. Such short circuits in a nonaqueous solvent can trigger runaway reactions, which raises safety concerns. In an effort to limit dendrite formation on the lithium–metal anode, the “self-healing” electrostatic shield mechanism (SHES) incorporates a small fraction of cesium salts in the electrolyte. These cesium ions remain charged on the surface, migrating toward the dendrites. The migration of Cs-ions to the dendrite surface creates a charged shield that compels lithium ions to deposit outside the dendrites, preventing the dendrite’s undesirable growth. To delve deeper into the working of the SHES mechanism, this study specifically utilizes Li and Cs atoms in both solvated and non-solvated configurations. These atoms are employed to be adsorbed onto various sites of the Li slab surface. Density functional theory (DFT) calculations are employed to explore the adsorption energy of Cs ions on Li-metal and their relationship with dendrite formation. In the presence of the solid electrolyte interphase (SEI), Cs ions migrate to damaged areas, depositing over the exposed bare metal surface and grain boundaries. When the SEI breaks, Cs ions cover the exposed Li surface, creating a positively charged shield in the exposed area, thereby reducing the pathway for Li plating and subsequent dendrite growth.
Marinho, Enesio; Villegas, Cesar E. P.; Venezuela, Pedro; Rocha, Alexandre Reily
Many-Body Effects on Electronic Properties and Optical Response of Single-Layer Penta-NiN2 for Infrared Optoelectronics Journal Article
Em: ACS Appl. Nano Mater., 2024, ISSN: 2574-0970.
@article{Marinho2024,
title = {Many-Body Effects on Electronic Properties and Optical Response of Single-Layer Penta-NiN2 for Infrared Optoelectronics},
author = {Enesio Marinho and Cesar E. P. Villegas and Pedro Venezuela and Alexandre Reily Rocha},
url = {https://pubs.acs.org/doi/full/10.1021/acsanm.4c03019},
doi = {10.1021/acsanm.4c03019},
issn = {2574-0970},
year = {2024},
date = {2024-08-15},
urldate = {2024-08-15},
journal = {ACS Appl. Nano Mater.},
publisher = {American Chemical Society (ACS)},
abstract = {We present a comprehensive first-principles study on the optoelectronic properties of the single-layer nickel diazenide (penta-NiN2), a pentagon-based 2D semiconductor with ideal Cairo tessellation, whose bulk counterpart has been recently synthesized. To address its quasiparticle band structure and excitonic effects on its optical absorption spectrum, we carry out ab initio calculations based on many-body perturbation theory within the GW-Bethe–Salpeter equation (BSE) framework. Our results reveal a quasiparticle band gap of 1.05 eV by employing the eigenvalue self-consistent GW approach, corroborating its potential in optoelectronics. The band gap exhibits an anomalous negative dependence on temperature, verified through the band gap pressure coefficient. Acoustic phonon-limited scattering analyses indicate an ultrahigh hole mobility of ∼87 × 104 cm2 V–1 s–1 along the [010] direction. The most prominent absorption peak of monolayer penta-NiN2 is associated with resonant excitons, corresponding to transitions from the valence band maximum to conduction band minimum + 2, which is explained by analyzing the state symmetry of the band edges. Hence, this pentagonal 2D semiconductor exhibits compelling and promising properties deserving deeper exploration in infrared optoelectronics and high-speed devices.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We present a comprehensive first-principles study on the optoelectronic properties of the single-layer nickel diazenide (penta-NiN2), a pentagon-based 2D semiconductor with ideal Cairo tessellation, whose bulk counterpart has been recently synthesized. To address its quasiparticle band structure and excitonic effects on its optical absorption spectrum, we carry out ab initio calculations based on many-body perturbation theory within the GW-Bethe–Salpeter equation (BSE) framework. Our results reveal a quasiparticle band gap of 1.05 eV by employing the eigenvalue self-consistent GW approach, corroborating its potential in optoelectronics. The band gap exhibits an anomalous negative dependence on temperature, verified through the band gap pressure coefficient. Acoustic phonon-limited scattering analyses indicate an ultrahigh hole mobility of ∼87 × 104 cm2 V–1 s–1 along the [010] direction. The most prominent absorption peak of monolayer penta-NiN2 is associated with resonant excitons, corresponding to transitions from the valence band maximum to conduction band minimum + 2, which is explained by analyzing the state symmetry of the band edges. Hence, this pentagonal 2D semiconductor exhibits compelling and promising properties deserving deeper exploration in infrared optoelectronics and high-speed devices.
Villegas, Cesar E. P.; Marinho, Enesio; Venezuela, Pedro; Rocha, Alexandre Reily
Optical spectra and exciton radiative lifetimes in bulk transition metal dichalcogenides Journal Article
Em: Phys. Chem. Chem. Phys., pp. -, 2024.
@article{D3CP05949A,
title = {Optical spectra and exciton radiative lifetimes in bulk transition metal dichalcogenides},
author = {Cesar E. P. Villegas and Enesio Marinho and Pedro Venezuela and Alexandre Reily Rocha},
url = {http://dx.doi.org/10.1039/D3CP05949A},
doi = {10.1039/D3CP05949A},
year = {2024},
date = {2024-04-16},
urldate = {2024-01-01},
journal = {Phys. Chem. Chem. Phys.},
pages = {-},
publisher = {The Royal Society of Chemistry},
abstract = {The optical response of layered transition metal dichalcogenides (TMDCs) exhibits remarkable excitonic properties which are important from both fundamental and device application viewpoints. One of these phenomena is the observation of intralayer/interlayer excitons. While much effort has been done to characterize excitons in monolayer TMDCs and their heterostructures, a quite limited number of works have addressed the exciton spectra of their bulk counterparts. In this work, we employ ab initio many-body perturbation calculations to investigate the exciton dynamics and spectra of bulk 2H-MX2 (M = Mo, W, and X = S, Se). For molybdenum-based systems, we find the presence of interlayer excitons at energies higher than the first bright exciton (XA), with non-negligible strength intensity. Our results also show that interlayer excitons in tungsten-based systems are almost degenerate in energy with XA and possess very small oscillator strengths when compared with molybdenum-based systems. At room temperature, and considering the thermal exciton fine-structure population for the XA-exciton, we estimate effective radiative lifetimes in the range of ∼4–14 ns. For higher energy excitons we predict longer effective lifetimes of tens of nanoseconds.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The optical response of layered transition metal dichalcogenides (TMDCs) exhibits remarkable excitonic properties which are important from both fundamental and device application viewpoints. One of these phenomena is the observation of intralayer/interlayer excitons. While much effort has been done to characterize excitons in monolayer TMDCs and their heterostructures, a quite limited number of works have addressed the exciton spectra of their bulk counterparts. In this work, we employ ab initio many-body perturbation calculations to investigate the exciton dynamics and spectra of bulk 2H-MX2 (M = Mo, W, and X = S, Se). For molybdenum-based systems, we find the presence of interlayer excitons at energies higher than the first bright exciton (XA), with non-negligible strength intensity. Our results also show that interlayer excitons in tungsten-based systems are almost degenerate in energy with XA and possess very small oscillator strengths when compared with molybdenum-based systems. At room temperature, and considering the thermal exciton fine-structure population for the XA-exciton, we estimate effective radiative lifetimes in the range of ∼4–14 ns. For higher energy excitons we predict longer effective lifetimes of tens of nanoseconds.
Gontijo, Rafael N.; Moutinho, Marcus V. O.; Righi, Ariete; Chiu, Po-Wen; Venezuela, Pedro; Pimenta, Marcos A.
Resonant enhancement of the 2G Raman band in twisted bilayer graphene Journal Article
Em: Materials Chemistry and Physics, pp. 129279, 2024, ISSN: 0254-0584.
@article{GONTIJO2024129279,
title = {Resonant enhancement of the 2G Raman band in twisted bilayer graphene},
author = {Rafael N. Gontijo and Marcus V. O. Moutinho and Ariete Righi and Po-Wen Chiu and Pedro Venezuela and Marcos A. Pimenta},
url = {https://www.sciencedirect.com/science/article/pii/S0254058424004048},
doi = {https://doi.org/10.1016/j.matchemphys.2024.129279},
issn = {0254-0584},
year = {2024},
date = {2024-04-12},
urldate = {2024-01-01},
journal = {Materials Chemistry and Physics},
pages = {129279},
abstract = {Raman spectroscopy is an extremely useful tool to characterize graphene systems. The strongest Raman features are the first-order G band and the second-order 2D and 2D′ bands, which are the overtones of the double resonance D and D’ bands. However, the 2G band, which is the overtone of the G band, is not usually observed in the spectra of monolayer graphene and of crystalline graphite. In this work, we present an experimental and theoretical investigation of the resonance Raman spectra in twisted bilayer graphene (TBG) with different twisting angles and using several laser excitation energies in the NIR and visible ranges. We observed that the 2G band is enhanced when the incident photons are in resonance with the transition between the van Hove singularities in the density of states of the TBG. We show that the 2G band has three contributions (2G1, 2G2 and 2G3), that are not dispersive by changing the laser excitation energy. We also present theoretical calculations showing that the 2G1 and 2G2 bands are related to combinations of the in-phase (IP) and out-of-phase (OP) vibrations of the atoms in the different layers. The Raman excitation profiles (REPs) of the 2G peaks are upshifted in comparison with the REP of the G band. This behavior was confirmed theoretically using a graphene tight binding model. We conclude that the different resonance behavior comes from the fact that the G band is a first-order process whereas the 2G band is second-order processes giving rise to overall different resonance conditions.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Raman spectroscopy is an extremely useful tool to characterize graphene systems. The strongest Raman features are the first-order G band and the second-order 2D and 2D′ bands, which are the overtones of the double resonance D and D’ bands. However, the 2G band, which is the overtone of the G band, is not usually observed in the spectra of monolayer graphene and of crystalline graphite. In this work, we present an experimental and theoretical investigation of the resonance Raman spectra in twisted bilayer graphene (TBG) with different twisting angles and using several laser excitation energies in the NIR and visible ranges. We observed that the 2G band is enhanced when the incident photons are in resonance with the transition between the van Hove singularities in the density of states of the TBG. We show that the 2G band has three contributions (2G1, 2G2 and 2G3), that are not dispersive by changing the laser excitation energy. We also present theoretical calculations showing that the 2G1 and 2G2 bands are related to combinations of the in-phase (IP) and out-of-phase (OP) vibrations of the atoms in the different layers. The Raman excitation profiles (REPs) of the 2G peaks are upshifted in comparison with the REP of the G band. This behavior was confirmed theoretically using a graphene tight binding model. We conclude that the different resonance behavior comes from the fact that the G band is a first-order process whereas the 2G band is second-order processes giving rise to overall different resonance conditions.
2023
au2, Enesio Marinho Jr.; Villegas, Cesar E. P.; Venezuela, Pedro; Rocha, Alexandre Reily
Photovoltaic efficiency of transition metal dichalcogenides thin films by ab initio excited-state methods Working paper
2023.
@workingpaper{marinho2023photovoltaic,
title = {Photovoltaic efficiency of transition metal dichalcogenides thin films by ab initio excited-state methods},
author = {Enesio Marinho Jr. au2 and Cesar E. P. Villegas and Pedro Venezuela and Alexandre Reily Rocha},
url = {https://arxiv.org/abs/2312.10284},
doi = {https://doi.org/10.48550/arXiv.2312.10284},
year = {2023},
date = {2023-12-16},
urldate = {2023-01-01},
abstract = {Transition metal dichalcogenides (TMDCs) have garnered significant interest in optoelectronics, owing to their scalability and thickness-dependent electrical and optical properties. In particular, thin films of TMDCs could be used in photovoltaic devices. In this work, we employ ab initio many-body perturbation theory within G0W0-BSE approach to accurately compute the optoelectronic properties of thin films of 2H-TMDCs composed of Mo, W, S, and Se. Subsequently, we evaluate their photovoltaic performance including exciton recombination effects, and show this is a key ingredient. We obtain efficiencies of up to 29% for a 200-nm thick film of ceWSe2, thus providing an upper limit. We also include other textcolorblackphenomenological recombination mechanisms that could be present in current samples. This slightly reduces efficiencies, indicating that even with current synthesis technologies, there is still potential for further enhancement of TMDCs' performance in photovoltaic applications.},
keywords = {},
pubstate = {published},
tppubtype = {workingpaper}
}
Transition metal dichalcogenides (TMDCs) have garnered significant interest in optoelectronics, owing to their scalability and thickness-dependent electrical and optical properties. In particular, thin films of TMDCs could be used in photovoltaic devices. In this work, we employ ab initio many-body perturbation theory within G0W0-BSE approach to accurately compute the optoelectronic properties of thin films of 2H-TMDCs composed of Mo, W, S, and Se. Subsequently, we evaluate their photovoltaic performance including exciton recombination effects, and show this is a key ingredient. We obtain efficiencies of up to 29% for a 200-nm thick film of ceWSe2, thus providing an upper limit. We also include other textcolorblackphenomenological recombination mechanisms that could be present in current samples. This slightly reduces efficiencies, indicating that even with current synthesis technologies, there is still potential for further enhancement of TMDCs' performance in photovoltaic applications.
Bertolini, Samuel; Venezuela, Pedro; Delcorte, Arnaud
The effect of lithium battery overpotential on sulfurized-polyacrylonitrile (SPAN): A theoretical approach Journal Article
Em: Journal of Energy Storage, vol. 78, pp. 110049, 2023, ISSN: 2352-152X.
@article{BERTOLINI2024110049,
title = {The effect of lithium battery overpotential on sulfurized-polyacrylonitrile (SPAN): A theoretical approach},
author = {Samuel Bertolini and Pedro Venezuela and Arnaud Delcorte},
url = {https://www.sciencedirect.com/science/article/pii/S2352152X23034485},
doi = {https://doi.org/10.1016/j.est.2023.110049},
issn = {2352-152X},
year = {2023},
date = {2023-12-14},
urldate = {2024-01-01},
journal = {Journal of Energy Storage},
volume = {78},
pages = {110049},
abstract = {The use of SPAN as a positive electrode for lithium‑sulfur batteries (LiSB) has demonstrated that, the material preserves a high specific capacity for several cycles. Through the recharging cycle, e.g. in Li-ion batteries, overpotential reactions can occur and promote degradation of the electrode material. In this work, we investigate the overpotential reactions that may occur in the presence of SPAN and cyclized-polyacrylonitre (cPAN). To approach this, ab initio molecular dynamics (AIMD) was used, and depletion of electrons was created in the system, thus inducing overpotential reactions in SPAN and cPAN. The simulations indicate that overpotential reactions tend to degrade the system, enabling reactions between the polymer and the solvent, as well as generating new branches in the polymer due to interactions with solvent radicals. The presence of different salts can also impact the overpotential reactions either by reacting with the solvent or by necessitating higher overpotential values.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The use of SPAN as a positive electrode for lithium‑sulfur batteries (LiSB) has demonstrated that, the material preserves a high specific capacity for several cycles. Through the recharging cycle, e.g. in Li-ion batteries, overpotential reactions can occur and promote degradation of the electrode material. In this work, we investigate the overpotential reactions that may occur in the presence of SPAN and cyclized-polyacrylonitre (cPAN). To approach this, ab initio molecular dynamics (AIMD) was used, and depletion of electrons was created in the system, thus inducing overpotential reactions in SPAN and cPAN. The simulations indicate that overpotential reactions tend to degrade the system, enabling reactions between the polymer and the solvent, as well as generating new branches in the polymer due to interactions with solvent radicals. The presence of different salts can also impact the overpotential reactions either by reacting with the solvent or by necessitating higher overpotential values.
Jr., Enesio Marinho; Villegas, Cesar E. P.; Venezuela, Pedro; Rocha, Alexandre Reily
Many-body effects on the quasiparticle band structure and optical response of single-layer penta-NiN$_2$ Working paper
2023.
@workingpaper{marinho2023manybody,
title = {Many-body effects on the quasiparticle band structure and optical response of single-layer penta-NiN$_2$},
author = {Enesio Marinho Jr. and Cesar E. P. Villegas and Pedro Venezuela and Alexandre Reily Rocha},
url = {https://arxiv.org/abs/2312.06394},
doi = {https://doi.org/10.48550/arXiv.2312.06394},
year = {2023},
date = {2023-12-11},
urldate = {2023-12-11},
abstract = {We present a comprehensive first-principles study on the optoelectronic properties of the single-layer nickel diazenide (penta-NiN2), a recently synthesized Cairo pentagonal 2D semiconductor. We carry out ab initio calculations based on the density-functional theory (DFT) and many-body perturbation theory, within the framework of Green's functions, to describe the quasiparticle properties and analyze the excitonic effects on the optical properties of monolayer penta-NiN2. Our results reveal a quasiparticle band gap of approximately 1 eV within the eigenvalue self-consistent GW approach, corroborating the monolayer penta-NiN2's potential in optoelectronics. Remarkably, the acoustic phonon-limited carrier mobility for the monolayer penta-NiN2 exhibits an ultra-high hole mobility of 84×104 cm2/V⋅s. Furthermore, our findings indicate that the material's band gap exhibits an anomalous negative dependence on temperature. Despite being a two-dimensional material, monolayer penta-NiN2 presents resonant excitons in its most prominent absorption peak. Therefore, penta-NiN2 boasts compelling and promising properties that merit exploration in optoelectronics and high-speed devices.},
keywords = {},
pubstate = {published},
tppubtype = {workingpaper}
}
We present a comprehensive first-principles study on the optoelectronic properties of the single-layer nickel diazenide (penta-NiN2), a recently synthesized Cairo pentagonal 2D semiconductor. We carry out ab initio calculations based on the density-functional theory (DFT) and many-body perturbation theory, within the framework of Green's functions, to describe the quasiparticle properties and analyze the excitonic effects on the optical properties of monolayer penta-NiN2. Our results reveal a quasiparticle band gap of approximately 1 eV within the eigenvalue self-consistent GW approach, corroborating the monolayer penta-NiN2's potential in optoelectronics. Remarkably, the acoustic phonon-limited carrier mobility for the monolayer penta-NiN2 exhibits an ultra-high hole mobility of 84×104 cm2/V⋅s. Furthermore, our findings indicate that the material's band gap exhibits an anomalous negative dependence on temperature. Despite being a two-dimensional material, monolayer penta-NiN2 presents resonant excitons in its most prominent absorption peak. Therefore, penta-NiN2 boasts compelling and promising properties that merit exploration in optoelectronics and high-speed devices.
Martins, Luiz G. Pimenta; Ruiz-Tijerina, David A.; Occhialini, Connor A.; Park, Ji-Hoon; Song, Qian; Lu, Ang-Yu; Venezuela, Pedro; Cançado, Luiz G.; Mazzoni, Mário S. C.; Matos, Matheus J. S.; Kong, Jing; Comin, Riccardo
Pressure tuning of minibands in MoS2/WSe2 heterostructures revealed by moiré phonons Journal Article
Em: Nat. Nanotechnol., 2023, ISSN: 1748-3395.
@article{PimentaMartins2023,
title = {Pressure tuning of minibands in MoS2/WSe2 heterostructures revealed by moiré phonons},
author = {Luiz G. Pimenta Martins and David A. Ruiz-Tijerina and Connor A. Occhialini and Ji-Hoon Park and Qian Song and Ang-Yu Lu and Pedro Venezuela and Luiz G. Cançado and Mário S. C. Mazzoni and Matheus J. S. Matos and Jing Kong and Riccardo Comin},
doi = {10.1038/s41565-023-01413-3},
issn = {1748-3395},
year = {2023},
date = {2023-06-15},
journal = {Nat. Nanotechnol.},
publisher = {Springer Science and Business Media LLC},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Rodrigues, Debora C. M.; Amorim, Rodrigo G.; Latgé, A.; Venezuela, Pedro
Improving the sensitivity of graphyne nanosensor by transition metal doping Journal Article
Em: Carbon, vol. 212, pp. 118087, 2023, ISSN: 0008-6223.
@article{RODRIGUES2023118087,
title = {Improving the sensitivity of graphyne nanosensor by transition metal doping},
author = {Debora C. M. Rodrigues and Rodrigo G. Amorim and A. Latgé and Pedro Venezuela},
url = {https://www.sciencedirect.com/science/article/pii/S0008622323003329},
doi = {https://doi.org/10.1016/j.carbon.2023.118087},
issn = {0008-6223},
year = {2023},
date = {2023-01-01},
journal = {Carbon},
volume = {212},
pages = {118087},
abstract = {The concern with air quality and safety urges for design and development of new gas sensors. Graphyne presents comparable electronic mobility and mechanical properties to graphene, with the advantage of naturally allowing single-atom dispersion into acetylenic pores. Therefore, we investigate the detection ability of transition metal (TM: Fe and Ni) doped graphyne (Gy) toward CO, NO, NO2, and CO2 gas molecules. Our aim is to engineer the electronic characteristics and further improve the sensing properties. We model the sensing device using TM-doped Gy nanoribbons (TM-GyNR) using density functional theory combined with non-equilibrium Green’s functions. Most of the gases presented chemical adsorption on the TM-GyNR, with slightly weaker interaction for gas/NiGyNR systems than gas/FeGyNR. These differences produced recovery times compatible with room temperature detectors for CO and NO (NiGyNR) and CO2 (FeGyNR) gases. We obtain gas sensitivity as high as 117% for CO/FeGyNR and 300% for NO2/NiGyNR. Due to mutual differences in binding energies and sensitivity among the gases, NiGyNR and FeGyNR also present high selectivity to distinguish the target molecules. Finally, our findings suggest that TM functionalization of graphynes is a promising strategy for engineering the sensitivity of gas nanosensors.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The concern with air quality and safety urges for design and development of new gas sensors. Graphyne presents comparable electronic mobility and mechanical properties to graphene, with the advantage of naturally allowing single-atom dispersion into acetylenic pores. Therefore, we investigate the detection ability of transition metal (TM: Fe and Ni) doped graphyne (Gy) toward CO, NO, NO2, and CO2 gas molecules. Our aim is to engineer the electronic characteristics and further improve the sensing properties. We model the sensing device using TM-doped Gy nanoribbons (TM-GyNR) using density functional theory combined with non-equilibrium Green’s functions. Most of the gases presented chemical adsorption on the TM-GyNR, with slightly weaker interaction for gas/NiGyNR systems than gas/FeGyNR. These differences produced recovery times compatible with room temperature detectors for CO and NO (NiGyNR) and CO2 (FeGyNR) gases. We obtain gas sensitivity as high as 117% for CO/FeGyNR and 300% for NO2/NiGyNR. Due to mutual differences in binding energies and sensitivity among the gases, NiGyNR and FeGyNR also present high selectivity to distinguish the target molecules. Finally, our findings suggest that TM functionalization of graphynes is a promising strategy for engineering the sensitivity of gas nanosensors.
Carozo, Victor; Carvalho, Bruno R.; Safeer, Syed Hamza; Seixas, Leandro; Venezuela, Pedro; Terrones, Mauricio
Raman spectroscopy of a few layers of bismuth telluride nanoplatelets Journal Article
Em: Nanoscale Adv., 2023, ISSN: 2516-0230.
@article{Carozo2023,
title = {Raman spectroscopy of a few layers of bismuth telluride nanoplatelets},
author = {Victor Carozo and Bruno R. Carvalho and Syed Hamza Safeer and Leandro Seixas and Pedro Venezuela and Mauricio Terrones},
doi = {10.1039/d3na00585b},
issn = {2516-0230},
year = {2023},
date = {2023-01-01},
journal = {Nanoscale Adv.},
publisher = {Royal Society of Chemistry (RSC)},
abstract = {<jats:p>Exploring the art of tailoring electronic and phonon properties in a few layers of Bi<jats:sub>2</jats:sub>Te<jats:sub>3</jats:sub> crystals through layer variation with Raman spectroscopy.</jats:p>},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
<jats:p>Exploring the art of tailoring electronic and phonon properties in a few layers of Bi<jats:sub>2</jats:sub>Te<jats:sub>3</jats:sub> crystals through layer variation with Raman spectroscopy.</jats:p>
2018
Rocha, C. G.; Rocha, A. R.; Venezuela, P.; Garcia, J. H.; Ferreira, M. S.
Finite-size correction scheme for supercell calculations in Dirac-point two-dimensional materials Journal Article
Em: Sci Rep, vol. 8, não 1, 2018, ISSN: 2045-2322.
@article{Rocha2018,
title = {Finite-size correction scheme for supercell calculations in Dirac-point two-dimensional materials},
author = {C. G. Rocha and A. R. Rocha and P. Venezuela and J. H. Garcia and M. S. Ferreira},
doi = {10.1038/s41598-018-27632-6},
issn = {2045-2322},
year = {2018},
date = {2018-12-01},
journal = {Sci Rep},
volume = {8},
number = {1},
publisher = {Springer Science and Business Media LLC},
abstract = {<jats:title>Abstract</jats:title><jats:p>Modern electronic structure calculations are predominantly implemented within the super cell representation in which unit cells are periodically arranged in space. Even in the case of non-crystalline materials, defect-embedded unit cells are commonly used to describe doped structures. However, this type of computation becomes prohibitively demanding when convergence rates are sufficiently slow and may require calculations with very large unit cells. Here we show that a hitherto unexplored feature displayed by several 2D materials may be used to achieve convergence in formation- and adsorption-energy calculations with relatively small unit-cell sizes. The generality of our method is illustrated with Density Functional Theory calculations for different 2D hosts doped with different impurities, all of which providing accuracy levels that would otherwise require enormously large unit cells. This approach provides an efficient route to calculating the physical properties of 2D systems in general but is particularly suitable for Dirac-point materials doped with impurities that break their sublattice symmetry.</jats:p>},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
<jats:title>Abstract</jats:title><jats:p>Modern electronic structure calculations are predominantly implemented within the super cell representation in which unit cells are periodically arranged in space. Even in the case of non-crystalline materials, defect-embedded unit cells are commonly used to describe doped structures. However, this type of computation becomes prohibitively demanding when convergence rates are sufficiently slow and may require calculations with very large unit cells. Here we show that a hitherto unexplored feature displayed by several 2D materials may be used to achieve convergence in formation- and adsorption-energy calculations with relatively small unit-cell sizes. The generality of our method is illustrated with Density Functional Theory calculations for different 2D hosts doped with different impurities, all of which providing accuracy levels that would otherwise require enormously large unit cells. This approach provides an efficient route to calculating the physical properties of 2D systems in general but is particularly suitable for Dirac-point materials doped with impurities that break their sublattice symmetry.</jats:p>
