arXiv subjects

Flavio Bento de Oliveira

Publications and source records attributed to Flavio Bento de Oliveira.

4 recordsLinked to original sources

arXiv2026

Transition-Metal Chalcogenide Nanowires: A First-Principles Study of Stability, Electronic Structure, and Mechanical Response

Subnanometer transition-metal chalcogenide nanowires provide a one-dimensional platform in which electronic functionality and mechanical response can be tuned through chemical composition. Here, density functional theory calculations are combined with machine-learning force-field (MLFF) molecular dynamics to investigate MoS, MoSe, MoTe, WS, WSe, and WTe nanowires. The optimized structures are dynamically stable within the harmonic approximation, and their electronic character evolves systematically across the chalcogen series: MoS, MoSe, WS, and WSe are metallic, whereas MoTe and WTe are semiconducting, with HSE06 band gaps of 0.52 and 0.20 eV, respectively. The effective axial stiffness decreases from sulfides to selenides and tellurides, consistent with the increase in metal--chalcogen bond length; using a circular effective cross section, the corresponding Young moduli range from 392 to 718 GPa. All six nanowires have negative formation energies relative to the selected elemental reference phases. MLFF trajectories extending to 2.5 ns at 300 K preserve the one-dimensional morphology and local atomic order, providing evidence of finite-temperature dynamical stability on the simulated time scale. The corresponding MLFF molecular-dynamics energy traces are shown in. We further examine the response of the nanowires to axial strain and curvature, including strain-induced band-gap modulation in the tellurides. These results establish composition and mechanical deformation as complementary routes for tuning the electronic and mechanical properties of ultrathin transition-metal chalcogenide nanowires and support their further investigation as components of flexible nanoelectronic systems.

cond-mat.mtrl-sci↗

arXiv2026

Hydrogen storage in pristine and Janus transition-metal dichalcogenide monolayers: electronic origins, coverage effects, and finite-temperature stability

Here, we present a systematic first-principles study of hydrogen adsorption on pristine and Janus MX2 and MSSe monolayers (M = Ni, Pd, Pt; X = S, Se), combining density-functional theory (DFT) calculations with finite-temperature ab initio molecular dynamics simulations (AIMD). Orbital-resolved electronic-structure analysis reveals that hydrogen binding strength is controlled primarily by the contribution of metal d states near the Fermi level, which increases from Pd and Pt to Ni. Chalcogen substitution from S to Se further modulates adsorption by enhancing surface polarizability. Structure plays a decisive role: metallic 1T phases promote stronger single-molecule adsorption due to enhanced electronic screening, whereas the more open coordination of the 2H phase provides greater configurational freedom at high hydrogen coverage. Janus functionalization introduces chemically inequivalent S- and Se-terminated surfaces, leading to side-dependent adsorption energies, hydrogen-layer thicknesses, and spatial distributions. Hydrogen uptake remains dominated by molecular physisorption across all systems. Finite-temperature AIMD simulations at 300 K demonstrate that hydrogen remains molecular even at high loadings, with no dissociation or irreversible chemisorption. 2H-NiSSe and 2H-PdSSe exhibit the most favorable combination of moderate adsorption energies, stable multilayer hydrogen configurations, and robust thermal stability, whereas Pt-based Janus systems display strong confinement and reduced reversibility. These results establish clear design principles for hydrogen storage in TMDs, showing that optimal performance arises from intermediate physisorption rather than maximal binding strength and highlighting Janus Ni- and Pd-based systems as promising platforms for reversible molecular hydrogen storage.

cond-mat.mtrl-sci↗

arXiv2023

Interaction of oxygen with pristine and defective MoS2 monolayers

Atom controlled sub-nanometer MoS$_2$ pores have been recently fabricated. Oxidative environments are of particular interest for MoS$_2$ applications in electronics, sensing and energy storage. In this work we carried out first-principles calculations of oxygen adsorption in plain and sub-nanometer MoS$_2$ nanopores. The chemical stability of the layers and pores towards oxygen was verified using density-functional theory. Dissociation and diffusion barriers have been calculated in order to understand surface and pore oxidation and its electronic properties at the atomic scale, which opens the path for future investigations of MoS$_2$ pores in a realistic environment.

cond-mat.mtrl-sci↗

arXiv2020

Exploring charge density distribution and electronic properties of hybrid organic-germanium layers

Band gap tuning and dielectric properties of small organic ligands adsorbed on bidimensional germanium monolayers (germanene) have been investigated using first-principles calculations. We show that the adsorption of these small groups retains the initially stable free-standing pristine buckled germanium nanostructures. Charge density and chemical bonding analysis show that the ligands are chemisorbed on the germanium layers. Finally we demosntrate that the dielectric properties of bare and ligand adsorbed germanene have a large anisotropy. Our findings of a finite gap shows open a path for rational design of nanostructures with possible applications in biosensors and solar cells.

cond-mat.mtrl-sci↗