Todas as Publicações do INCT-MI

@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 = {Electronic structure, Resonant Raman spectroscopy, Twisted bilayer graphene},

pubstate = {published},

tppubtype = {article}

}

@article{SOUSA2023111198,

title = {Pressure effect on the structural, electronic, and magnetic properties of the battery cathode material LiMn2O4: An ab-initio study},

author = {O. M. Sousa and F. Sorgenfrei and L. V. C. Assali and M. V. Lalic and Angela B. Klautau and P. Thunström and C. M. Araujo and O. Eriksson and H. M. Petrilli},

url = {https://www.sciencedirect.com/science/article/pii/S0022369722006151},

doi = {https://doi.org/10.1016/j.jpcs.2022.111198},

issn = {0022-3697},

year  = {2023},

date = {2023-01-01},

urldate = {2023-01-01},

journal = {Journal of Physics and Chemistry of Solids},

volume = {175},

pages = {111198},

abstract = {LiMn2O4 is a battery cathode material with desirable properties such as low cost, low toxicity, high natural abundance of Mn, and environmental compatibility. By means of first-principles calculations, we study the structural, magnetic, and electronic properties of LiMn2O4 under ambient conditions and high hydrostatic pressures (until 20 GPa). We obtain two oxidation states for Mn, even using a cubic structure, which differ in all analyzed properties: structural, electronic, and magnetic. At P > 0, such properties were found to display a standard behavior decreasing smoothly and linearly with pressure. Furthermore, the enthalpy of cubic and orthorhombic structures under low and high-pressure conditions were examined, showing that no cubic to orthorhombic phase transition exists in all the investigated pressure range, nor is a magnetic cubic to a non-magnetic cubic phase transition possible.},

keywords = {Cathode materials, Electronic structure, LiMnO under pressure},

pubstate = {published},

tppubtype = {article}

}

@article{SOUZA2023108460,

title = {Benchmarking DFT functionals for photophysics of pyranoflavylium cations},

author = {Jhonathan R. Souza and Carles Curutchet and Yuri A. Aoto and Paula Homem-De-Mello},

url = {https://www.sciencedirect.com/science/article/pii/S109332632300058X},

doi = {https://doi.org/10.1016/j.jmgm.2023.108460},

issn = {1093-3263},

year  = {2023},

date = {2023-01-01},

journal = {Journal of Molecular Graphics and Modelling},

volume = {122},

pages = {108460},

abstract = {An intense absorption, phosphorescence, a long triplet excited state lifetime and singlet oxygen generation capabilities are characteristics of pyranoflavylium cations, analogues to pyranoanthocyanidins originated in the maturation process of red wine. Such properties make these compounds potential photosensitizers to be applied in photodynamic therapy. In this context, the photophysical processes underlying that treatment critically depend on the electronic structure of the pyranoflavylium molecules. When employing density functional theory to describe the electronic structure of molecules, the choice of the most suitable functional is not trivial, and benchmark studies are needed to orient practitioners in the field. In this work, a benchmark of seven of the most commonly used density functionals in addressing the photophysical properties of a set of eight pyranoflavylium cations is reported. Ground and excited state geometries, molecular orbitals, and absorption, fluorescence and phosphorescence transition energies were calculated using density functional theory approaches, and evaluated and compared to experimental data and monoreferential wave function-based methodologies. Statistical analysis of the results indicates that global-hybrid functionals allow an excellent description of absorption and emission energies, with errors around 0.05 eV, while range-separated variants led to somewhat larger errors in the range 0.1–0.2 eV. In contrast, range-separated functionals display excellent phosphorescence energies with errors close to 0.05 eV, in this case global-hybrids showing increased discrepancies around 0.5–0.1 eV.},

keywords = {Benchmark, Electronic structure, Excited-states, Photophysics, Photosensitizers, Time-dependent density functional theory (TD-DFT)},

pubstate = {published},

tppubtype = {article}

}