Publicações de Alexandre Reily Rocha
Villegas, Cesar EP; Vasquez-Marcani, Aider; Rocha, Alexandre Reily Static dielectric response and screening in solid state physics: Why dimensionality matters in dielectrics Journal Article Em: American Journal of Physics, vol. 92, não 5, pp. 360–366, 2024. Resumo | Links | BibTeX | Tags: 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. Resumo | Links | BibTeX | Tags: Pedrosa, Renan Narciso; Villegas, Cesar EP; Rocha, Alexandre Reily; Amorim, Rodrigo G.; Scopel, Wanderlã L. Optical properties enhancement via WSSe/silicene solar cell junctions Journal Article Em: Energy Advances, vol. 3, não 4, pp. 821–828, 2024. Resumo | Links | BibTeX | Tags: Villegas, Cesar E. P.; Rocha, Alexandre Reily Screened hydrogen model of excitons in semiconducting nanoribbons Working paper 2024. Resumo | Links | BibTeX | Tags: 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. Resumo | Links | BibTeX | Tags: 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. Resumo | Links | BibTeX | Tags: Gomes-Filho, Márcio S.; Torres, Alberto; Rocha, Alexandre Reily; Pedroza, Luana S. Size and Quality of Quantum Mechanical Data Set for Training Neural Network Force Fields for Liquid Water Journal Article Em: The Journal of Physical Chemistry B, vol. 127, não 6, pp. 1422-1428, 2023, (PMID: 36730848). Resumo | Links | BibTeX | Tags: Padilha, Antonio Claudio Michejevs; Rocha, Alexandre Reily; Dalpian, Gustavo M. 17 – Ordered vacancy compounds: the case of the Mangéli phases of TiO2 Book Section Em: Kumar, Vijay; Som, Sudipta; Sharma, Vishal; Swart, Hendrik C. (Ed.): Metal Oxide Defects, pp. 533-565, Elsevier, 2023, ISBN: 978-0-323-85588-4. Resumo | Links | BibTeX | Tags: Computational simulation, Density functional theory, DFT, Magnéli phases, Memristive devices, Memristor, Titanium oxide Amorim, Felippe P.; Torres, Alberto; Villegas, Cesar E. P.; Rocha, Alexandre Reily Gate voltage enhances the thermoelectric transport of quantum dots in graphene nanoribbons Journal Article Em: Computational Materials Science, vol. 227, pp. 112207, 2023, ISSN: 0927-0256. Resumo | Links | BibTeX | Tags: 7-14-7 AGNR, Gate voltage enhances, Quantum dots in graphene, Thermoelectric transport2024
@article{villegas2024static,
title = {Static dielectric response and screening in solid state physics: Why dimensionality matters in dielectrics},
author = {Cesar EP Villegas and Aider Vasquez-Marcani and Alexandre Reily Rocha},
url = {https://pubs.aip.org/aapt/ajp/article-abstract/92/5/360/3283200/Static-dielectric-response-and-screening-in-solid?redirectedFrom=fulltext},
doi = {https://doi.org/10.1119/5.0122288},
year = {2024},
date = {2024-05-01},
urldate = {2024-01-01},
journal = {American Journal of Physics},
volume = {92},
number = {5},
pages = {360–366},
publisher = {AIP Publishing},
abstract = {Textbooks often present the phenomenon of screening within the Thomas–Fermi model for three-dimensional free electron gases, but obtaining the dielectric response function and screening potential for dielectric systems of reduced dimensionality is also of pedagogical interest. In this work, we introduce a simple approach to investigate static screening in dielectric systems in the presence of an impurity charge for different dimensionalities. This approach is applicable to semiconductors and insulators alike. We demonstrate that, in 3D systems, the macroscopic dielectric function in reciprocal space is a constant, while in 2D and 1D systems, it strongly depends on the momentum transferred to the electrons in the dielectric. Through the proposed dielectric screening model, one can also determine binding energies in a hydrogenic model that can be used to describe excitations in real semiconductor systems.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
@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}
}
@article{pedrosa2024optical,
title = {Optical properties enhancement via WSSe/silicene solar cell junctions},
author = {Renan Narciso Pedrosa and Cesar EP Villegas and Alexandre Reily Rocha and Rodrigo G. Amorim and Wanderlã L. Scopel},
url = {https://pubs.rsc.org/en/content/articlehtml/2024/ya/d3ya00529a},
doi = {10.1039/D3YA00529A},
year = {2024},
date = {2024-03-04},
urldate = {2024-03-04},
journal = {Energy Advances},
volume = {3},
number = {4},
pages = {821–828},
publisher = {Royal Society of Chemistry},
abstract = {2D Janus monolayers exhibit nanoscale asymmetric surface organization along the out-of-plane direction and have recently emerged as a class of 2D materials. In this work, we investigate the energetic, electronic, and optical properties of the vertical van der Waals stack between WSSe and silicene monolayers based on first-principles calculations. The Janus/silicene interface formation is driven by an exothermic process, and charge transfer from the silicene to the Janus monolayer is observed. The intrinsic properties of silicene and Janus are preserved despite the stacking of the parts. The Bethe–Salpeter equation (BSE) was used to understand the contact influence on the optical absorption spectrum of the vertical interface. Our findings reveal that the power conversion energy (PCE) of the heterostructure is boosted 2.42 times higher than that of the Janus monolayer. Thus, due to its PCE and transparent electrical contact, the heterojunction is a promising candidate for use as a photovoltaic device compared to its counterparts.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
@workingpaper{villegas2024screened,
title = {Screened hydrogen model of excitons in semiconducting nanoribbons},
author = {Cesar E. P. Villegas and Alexandre Reily Rocha},
url = {https://arxiv.org/abs/2403.15793},
doi = { https://doi.org/10.48550/arXiv.2403.15793},
year = {2024},
date = {2024-01-23},
urldate = {2024-01-01},
abstract = {The optical response of quasi-one-dimensional systems is often dominated by tightly bound excitons, that significantly influence their basic electronic properties. Despite their importance for device performance, accurately predicting their excitonic effects typically requires computationally demanding many-body approaches. Here, we present a simplified model to describe the static macroscopic dielectric function, which depends only on the width of the quasi-one-dimensional system and its polarizability per unit length. We show that at certain interaction distances, the screened Coulomb potential is greater than its bare counterpart, which results from the enhanced repulsive electron-electron interactions. As a test case, we study fourteen different nanoribbons, twelve of them armchair graphene nanoribbons of different families. Initially, we devised a simplified equation to estimate the exciton binding energy and extension that provides results comparable to those from the full Bethe-Salpeter equation, albeit for a specific nanoribbon family. Then, we used our proposed screening potential to solve the 1D Wannier-Mott equation, which turn out to be broad approach, that is able to predict binding energies that match quite well the ones obtained with the Bethe-Salpeter equation, irrespective of the nanoribbon family.},
keywords = {},
pubstate = {published},
tppubtype = {workingpaper}
}
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 ce{WSe2}, thus providing an upper limit. We also include other textcolor{black}{phenomenological} 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}
}
@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}
}
@article{doi:10.1021/acs.jpcb.2c09059,
title = {Size and Quality of Quantum Mechanical Data Set for Training Neural Network Force Fields for Liquid Water},
author = {Márcio S. Gomes-Filho and Alberto Torres and Alexandre Reily Rocha and Luana S. Pedroza},
url = {https://doi.org/10.1021/acs.jpcb.2c09059},
doi = {10.1021/acs.jpcb.2c09059},
year = {2023},
date = {2023-01-01},
journal = {The Journal of Physical Chemistry B},
volume = {127},
number = {6},
pages = {1422-1428},
abstract = {Molecular dynamics simulations have been used in different scientific fields to investigate a broad range of physical systems. However, the accuracy of calculation is based on the model considered to describe the atomic interactions. In particular, ab initio molecular dynamics (AIMD) has the accuracy of density functional theory (DFT) and thus is limited to small systems and a relatively short simulation time. In this scenario, Neural Network Force Fields (NNFFs) have an important role, since they provide a way to circumvent these caveats. In this work, we investigate NNFFs designed at the level of DFT to describe liquid water, focusing on the size and quality of the training data set considered. We show that structural properties are less dependent on the size of the training data set compared to dynamical ones (such as the diffusion coefficient), and a good sampling (selecting data reference for the training process) can lead to a small sample with good precision.},
note = {PMID: 36730848},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
@incollection{MICHEJEVSPADILHA2023533,
title = {17 - Ordered vacancy compounds: the case of the Mangéli phases of TiO2},
author = {Antonio Claudio Michejevs Padilha and Alexandre Reily Rocha and Gustavo M. Dalpian},
editor = {Vijay Kumar and Sudipta Som and Vishal Sharma and Hendrik C. Swart},
url = {https://www.sciencedirect.com/science/article/pii/B9780323855884000143},
doi = {https://doi.org/10.1016/B978-0-323-85588-4.00014-3},
isbn = {978-0-323-85588-4},
year = {2023},
date = {2023-01-01},
urldate = {2023-01-01},
booktitle = {Metal Oxide Defects},
pages = {533-565},
publisher = {Elsevier},
series = {Metal Oxides},
abstract = {Defects typically appear in materials in very limited quantities, usually of the order of 1016–1019/cm3. In some cases, however, these defects can be observed in a much larger concentration, enough to change the stoichiometry of the parent compound and even change their crystal structure. An important class of these materials is the ordered vacancy compounds, first proposed for CdIn2Se4. Other compounds, such as hybrid perovskites, can also present ordered vacancy compounds, such as Cs2SnI6, derived from CsSnI3. In this chapter, we will discuss ordered vacancy compounds derived from the transition metal oxide compound TiO2. These are known as the Magnéli phases of TiO2 and can be constructed by removing oxygen atoms from the host lattice. There are several different polymorphs that can be created by changing the quantity of oxygen vacancies, including Ti2O3, Ti3O5, and Ti4O7 (based on the formula TinO2n−1). We will discuss the structural determination of these materials that can be created by sliding planes from the rutile TiO2 structure. Also, the electronic structure of these compounds is characteristic of intermediate band materials and can be directly correlated to the properties of oxygen vacancies in TiO2. Lastly, we will discuss the potential applications of this kind of materials that can include memristors and batteries.},
keywords = {Computational simulation, Density functional theory, DFT, Magnéli phases, Memristive devices, Memristor, Titanium oxide},
pubstate = {published},
tppubtype = {incollection}
}
@article{AMORIM2023112207,
title = {Gate voltage enhances the thermoelectric transport of quantum dots in graphene nanoribbons},
author = {Felippe P. Amorim and Alberto Torres and Cesar E. P. Villegas and Alexandre Reily Rocha},
url = {https://www.sciencedirect.com/science/article/pii/S092702562300201X},
doi = {https://doi.org/10.1016/j.commatsci.2023.112207},
issn = {0927-0256},
year = {2023},
date = {2023-01-01},
urldate = {2023-01-01},
journal = {Computational Materials Science},
volume = {227},
pages = {112207},
abstract = {Chemically derived graphene nanoribbons and quantum dots are unique nanostructures that offer more possibilities than 2D and 3D systems to tune their electronic properties due to the enhanced quantum confinement effects. This feature make them potential candidates for many technological applications, including thermoelectrics. In this work, we combined density functional theory calculations with the non-equilibrium Green’s function formalism to investigate the electronic and thermoelectric properties of recently synthesized quantum dots in graphene nanoribbons under the presence of an applied gate voltage, and for different temperatures. We find that the electronic states at the band edge are highly localized in the inner region of the quantum dot, and can be lifted to higher energies by applying a gate voltage, which subsequently enhances figure of merit. Moreover, at zero gate voltage and room temperature, we estimate the lower bound for ZT to be approximately 0.25. Interestingly, this lower bound can exceed unity by smoothly increasing the gate voltage for values above 6 V. The overall results regarding the enhancement of ZT suggest that quantum dots in graphene nanoribbons would be promising candidates for thermoelectric applications.},
keywords = {7-14-7 AGNR, Gate voltage enhances, Quantum dots in graphene, Thermoelectric transport},
pubstate = {published},
tppubtype = {article}
}
