arXiv subjects

Marcelo L. Pereira Junior

Publications and source records attributed to Marcelo L. Pereira Junior.

24 records · Page 2Linked to original sources

arXiv2024

Structural and Electronic Properties of Amorphous Silicon and Germanium Monolayers and Nanotubes: A DFT Investigation

A recent breakthrough has been achieved by synthesizing monolayer amorphous carbon (MAC), which introduces a material with unique optoelectronic properties. Here, we used ab initio (DFT) molecular dynamics simulations to study silicon and germanium MAC analogs. Typical unit cells contain more than 600 atoms. We also considered their corresponding nanotube structures. The cohesion energy values for MASi and MAGe range from -8.41 to -7.49 eV/atom and follow the energy ordering of silicene and germanene. Their electronic behavior varies from metallic to small band gap semiconductors. Since silicene, germanene, and MAC have already been experimentally realized, the corresponding MAC-like versions we propose are within our present synthetic capabilities.

cond-mat.mtrl-sci↗

arXiv2023

Exploring the Elastic Properties and Fracture Patterns of Me-Graphene Monolayers and Nanotubes through Reactive Molecular Dynamics Simulations

Me-graphene (MeG) is a novel two-dimensional (2D) carbon allotrope. Due to its attractive electronic and structural properties, it is important to study the mechanical behavior of MeG in its monolayer and nanotube topologies. In this work, we conducted fully atomistic reactive molecular dynamics simulations using the Tersoff force field to investigate their mechanical properties and fracture patterns. Our results indicate that Young's modulus of MeG monolayers is about 414 GPa and in the range of 421-483 GPa for the nanotubes investigated here. MeG monolayers and MeGNTs directly undergo from elastic to complete fracture under critical strain without a plastic regime.

cond-mat.mtrl-sci↗

arXiv2023

Elastocaloric Effect in Graphene Kirigami

Kirigami, a traditional Japanese art of paper-cutting, has recently been explored for its elastocaloric effect (ECE) in kirigami-based materials (KMs), where applying strain induces temperature changes. In this study, we investigate the ECE in a nanoscale graphene kirigami (GK) monolayer, representing the thinnest possible KM, to better understand this phenomenon. Through molecular dynamics simulations, we analyze the temperature change and coefficient of performance (COP) of the nanoscale GK architecture. Our findings reveal that while GKs lack the intricate temperature changes observed in macroscopic KMs, they exhibit a substantial temperature change of approximately 9.32 K (23 times higher than that of macroscopic KMs, which is about 0.4K) for heating and -3.50 K for cooling. Additionally, they demonstrate reasonable COP values of approximately 1.57 and 0.62, respectively. It is noteworthy that the one-atom-thick graphene configuration prevents the occurrence of the complex temperature distribution observed in macroscopic KMs.

cond-mat.mtrl-sci↗

arXiv2023

On the Mechanical, Electronic, and Optical Properties of 8-16-4 Graphyne: A 2D Carbon Allotrope with Dirac Cones

Due to the success achieved by graphene, several 2D carbon-based allotropes were theoretically predicted and experimentally synthesized. We used density functional theory and reactive molecular dynamics simulations to investigate the mechanical, structural, electronic, and optical properties of 8-16-4 Graphyne. The results showed that this material exhibits good dynamical and thermal stabilities. Its formation energy and elastic moduli are -8.57 eV/atom and 262.37 GPa, respectively. This graphyne analogue is a semi-metal and presents two Dirac cones in its band structure. Moreover, it is transparent, and its intense optical activity is limited to the infrared region. Remarkably, the band structure of 8-16-4 Graphyne remains practically unchanged at even moderate strain regimes. As far as we know, this is the first 2D carbon allotrope to exhibit this behavior.

cond-mat.mtrl-sci↗

arXiv2020

Predicting the Energetic Stabilization of Janus-MoSSe/AlN Heterostructures: A DFT Study

The packing mechanisms between Janus-MoSSe and Aluminum-Nitride (AlN) sheets were systematically investigated by using Density Function Theory calculations. Results show that the stabilization (packing) energies vary from -35.5 up to -17.5 meV depending on the chemical species involved in the interface. The packing energies were obtained using the improved Lennard-Jones (ILJ) potential. The SeMoS/AlN heterostructures, when the MoS face is interacting with the AlN sheet, presented the lowest packing energies due to the sulfur's higher degree of reactivity. Importantly, the calculated bandgap values ranged within the interval 1.61-1.87 eV, which can be interesting for photovoltaic applications.

cond-mat.mtrl-sci↗

arXiv2020

Intrinsic Properties of Bipolarons in Armchair Graphene Nanoribbons

We performed an investigation concerning bipolaron dynamics in armchair graphene nanoribbons (AGNRs) under the influence of different electric field and electron-phonon coupling regimes. By studying the response to the electric excitation, we were able to determine the effective mass and terminal velocity of this quasiparticle in AGNRs. Remarkably, bipolarons in narrower AGNRs move as fast as the ones in conjugated polymers. Our findings pave the way to enhance the understanding of the behavior of charge carriers in graphene nanoribbons.

cond-mat.mtrl-sci↗