Computer study of the physical properties of a copper film on a heated graphene surface

The structural, kinetic, and mechanical properties of a copper film deposited on single-layer and two-layer graphenes have been studied in a molecular-dynamics model in the temperature range 300 K ≤ T ≤ 3300 K. The film sizes are reduced in the "zigzag" direction more slowly than in the "armchair" direction. The differences have been found to appear in the behavior of copper atoms on single-layer and two-layer graphenes with increasing temperature. Copper atoms on the two-layer graphene have higher horizontal mobility over entire temperature range. However, Cu atoms on the single-layer graphene become more mobile in the vertical direction beginning from a temperature of ~1500 K. The stress tensor components of the copper film characterizing the action of forces on the horizontal areas have a sharp extremum at T = 1800 K in the case of the single-layer graphene and are characterized by quite smooth behavior in the case of the two-layer graphene. © 2013 Pleiades Publishing, Ltd

Computer simulation of thin nickel films on single-layer graphene

The energy, mechanical, and transport properties of nickel films on a single-layer graphene sheet in the temperature range 300 K ≤ T ≤ 3300 K have been investigated using the molecular dynamics method. The stresses generated in the plane of the metallic film are significantly enhanced upon deposition of another nickel film on the reverse side of the graphene sheet. In this case, the self-diffusion coefficient in the film plane above 1800 K, in contrast, decreases. An appreciable temperature elongation per unit length of the film also occurs above 1800 K and dominates in the "zigzag" direction of the graphene sheet. The vibrational spectra of the nickel films on single-layer graphene for horizontal and vertical displacements of the Ni atoms have very different shapes. © 2013 Pleiades Publishing, Ltd

Molecular dynamics simulation of compression of single-layer graphene

The compression of a single-layer graphene sheet in the "zigzag" and "armchair" directions has been investigated using the molecular dynamics method. The distributions of the xy and yx stress components are calculated for atomic chains forming the graphene sheet. A graphene sheet stands significant compressive stresses in the "zigzag" direction and retains its integrity even at a strain of ∼0.35. At the same time, the stresses which accompany the compressive deformation of single-layer graphene in the "armchair" direction are more than an order in magnitude lower than corresponding characteristics for the "zigzag" direction. A compressive strain of ∼0.35 in the "armchair" direction fractures the graphene sheet into two parts. © 2013 Pleiades Publishing, Ltd

Physical aspects of the lithium ion interaction with the imperfect silicene located on a silver substrate

Epitaxy of Si on a silver substrate is the main method to obtain silicene. The latter does not separate from the substrate. In the present paper, the possibility of using silicene on a silver substrate as an anode for lithium-ion batteries is studied by the method of molecular dynamics. Structural and mechanical effects arising from the motion of a Li + ion through a planar channel formed by a perfect and defective two-layer silicene are studied. Generally, the defect stability and silicene sheet integrity are independent of the Ag(001) or Ag(111) substrate type. The transverse vibrations of Si atoms in the channel have a significant effect on the motion of lithium ions. This effect is taken into account by using the interference factor that describes the slowing down of the motion of the Li + ion in the channel. The dependence of this coefficient on the size of vacancy defects in silicene is determined. The presence of the substrate makes this dependence less relevant. The stress distribution in the defective silicene while driving a lithium ion along the planar silicene channel is calculated. The strongest stresses in the silicene are created by forces directed perpendicular to the strength of the external electric field. These forces dominate in the silicene channel placed on the substrates of both types. © 2018, Institute for Metals Superplasticity Problems of Russian Academy of Sciences. All rights reserved.Acknowledgements. This study is supported by the Russian Science Foundation (project no. 16‑13‑00061)

Diffusion of Oxygen in Hypostoichiometric Uranium Dioxide Nanocrystals. A Molecular Dynamics Simulation

Received: 04.02.2021. Revised: 30.03.2021. Accepted: 30.03.2021. Available online: 31.03.2021.This article belongs to the PCEE-2020 Special Issue.A molecular dynamic simulation of diffusion of intrinsic oxygen anions in the bulk of hypostoichiometric UO2-x nanocrystals with a free surface was carried out. The main diffusion mechanism turned out to be the migration of oxygen by the anionic vacancies. It is shown that in the range of values of the non-stoichiometry parameter 0.05 ≤x ≥ 0.275 the oxygen diffusion coefficient D is weakly dependent on temperature, despite the uniform distribution of the vacancies over the model crystallite. The reliable D values calculated for the temperature T = 923 K are in the range from 3∙10-9 to 7∙10-8 cm2/s, in quantitative agreement with the experimental data. The corresponding diffusion activation energy is in the range from 0.57 eV to 0.65 eV, depending on the interaction potentials used for the calculations.The work was financially supported by the State Atomic Energy Corporation Rosatom, state contract no. Н.4о.241.19.20.1048 dated 17.04.2020, identifier 17706413348200000540. S.K. Gupta thanks the Department of Science and Technology (India) and the Russian Foundation for Basic Research (Russia) for the financial support (Grant no.: INT/RUS/RFBR/IDIR/P-6/2016)

FIRST-PRINCIPLE STUDY OF THE TRITIUM BEHAVIOR IN A FLiBe MOLTEN SALT MIXTURE

This article presents the results of ab initio MD modeling and research of FLiBe molten salt at different temperatures and compositions. As a result, were obtained energetic characteristics of the system, made conclusions about the behavior of tritium and helium