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

Computer study of the structure and thermal stability of a monolayer mos2 film on a diamond substrate

MoS2 is a promising candidate for next-generation electrical and optoelectronic devices. The use of chemical vapor deposition allows obtaining high-quality MoS2 monolayers on a diamond substrate. However, it is not clear how firmly the MoS2 monolayer is held on the diamond substrate at a high temperature and how the structure of the MoS2 monolayer changes after its deposition on the diamond substrate and subsequent heating on it. In this paper, the molecular dynamics method is used to study the stability of single-layer MoS2 in the temperature range of 250 – 550 K. The molybdenum disulfide film on a diamond substrate structure is studied by constructing Voronoi polyhedra. Polyhedra were built around Mo atoms, and faces are formed by neighboring S atoms. The distributions of polyhedrons by the number of faces were found. These distributions were also calculated for truncated polyhedra obtained by eliminating small geometric elements. A comparison of the obtained statistical distributions for a MoS2 monolayer on a diamond substrate with the corresponding characteristics of an autonomous monolayer MoS2 indicates a significant change in the structure of the monolayer. This change is a result of its deposition on the diamond substrate. When the temperature reaches 550 K, the MoS2 film is completely separated from the substrate. There is a singularity near this temperature, which indicates the thermal instability of the system under investigation. © 2019, Institute for Metals Superplasticity Problems of Russian Academy of Sciences. All rights reserved

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

Molecular Dynamic Study of the Applicability of Silicene Lithium Ion Battery Anodes: A Review

Received: 29 March 2023. Accepted: 16 May 2023. Published online: 22 May 2023.Lithium-ion batteries (LIBs) are the main energy storage devices that have found wide application in the electrical, electronics, automotive and even aerospace industries. In practical applications, silicene has been put forward as an active anode material for LIBs. This is facilitated by its high theoretical capacitance, strength, and small volume change during lithiation. Thin-film materials containing two-layer silicene and intended for use in the LIB anode have been studied by the method of classical molecular dynamics. Among the important characteristics obtained is the fillability of the silicene anode (under the influence of an electric field), which was determined depending on the type of vacancy defects in silicene and the type of substrate used. Both metallic (Ag, Ni, Cu, Al) and non-metallic (graphite, silicon carbide) substrates are considered. The behavior of the self-diffusion coefficient of intercalated lithium atoms in a silicene channel as it is filled has been studied. Based on the construction of Voronoi polyhedra, the packing of lithium atoms and the state of the walls in the channel has been studied in detail. The change in the shape of silicene sheets, as well as the stresses in them caused by lithium intercalation, are analyzed. It has been established that two-layer silicene with monovacancies on a nickel substrate is the most optimal variant of the anode material. The results of this work may be useful in the development of new anode materials for new generation LIBs.This work is executed in the frame of the scientific theme of Institute of High-Temperature Electrochemistry UB RAS, number FUME–2022–0005, registration number 122020100205-5 and under agreement no. 075–03–2022–011 of 14 January, 2022 (FEUZ–2020–0037)

Computer Development of Silicene Anodes for Lithium-Ion Batteries: A Review

Received: 30 July 2022. Accepted: 30 September 2022.Lithium-ion batteries (LIB) have many advantages, the main ones being high energy density, long service life, small size, and low environmental pollution. This review is devoted to further development of LIBs based on quantum mechanical calculations in order to use them for energy storage in the future. Energetically favorite places occupied by lithium atoms on silicene are found. Lithium filling of free-standing two-layer silicene and single-layer silicene on graphene was studied. The geometric, energy, charging characteristics, as well as the open circuit voltage are determined. The effect of metallic (Al, Cu, Ni, Ag and Au) and non-metallic (C, SiC and BN) substrates on the geometric, energy and electronic properties of silicene has been studied. The effect of an intermediate nickel layer on the characteristics of the "silicene on a multilayer copper substrate" system has been studied. The effect of nuclear transmutation doping (NTD) of the silicene/graphite system with phosphorus on the density of electronic states of one- and two-layer silicene has been determined. Promising applications for silicene and the advantages of its use as an anode in a lithium-ion battery are discussed.This work is executed in the frame of the scientific theme of Institute of High-Temperature Electrochemistry UB RAS, number FUME-2022-0005, registration number 122020100205-5

Computational study of lithium intercalation in silicene channels on a carbon substrate after nuclear transmutation doping

Silicene is considered to be the most promising anode material for lithium-ion batteries. In this work, we show that transmutation doping makes silicene substantially more suitable for use as an anode material. Pristine and modified bilayer silicene was simulated on a graphite substrate using the classical molecular dynamics method. The parameters of Morse potentials for alloying elements were determined using quantum mechanical calculations. The main advantage of modified silicene is its low deformability during lithium intercalation and its possibility of obtaining a significantly higher battery charge capacity. Horizontal and vertical profiles of the density of lithium as well as distributions of the most significant stresses in the walls of the channels were calculated both in undoped and doped systems with different gaps in silicene channels. The energies of lithium adsorption on silicene, including phosphorus-doped silicene, were determined. High values of the self-diffusion coefficient of lithium atoms in the silicene channels were obtained, which ensured a high cycling rate. The calculations showed that such doping increased the normal stress on the walls of the channel filled with lithium to 67% but did not provoke a loss of mechanical strength. In addition, doping achieved a greater battery capacity and higher charging/discharging rates. © 2020 by the authors.Russian Science Foundation, RSF: 16-13-00061Funding: This work was supported by the Russian Science Foundation (grant number 16-13-00061)

Computer Test of a Modified Silicene/Graphite Anode for Lithium-Ion Batteries

Despite the considerable efforts made to use silicon anodes and composites based on them in lithium-ion batteries, it is still not possible to overcome the difficulties associated with low conductivity, a decrease in the bulk energy density, and side reactions. In the present work, a new design of an electrochemical cell, whose anode is made in the form of silicene on a graphite substrate, is presented. The whole system was subjected to transmutation neutron doping. The molecular dynamics method was used to study the intercalation and deintercalation of lithium in a phosphorus-doped silicene channel. The maximum uniform filling of the channel with lithium is achieved at 3% and 6% P-doping of silicene. The high mobility of Li atoms in the channel creates the prerequisites for the fast charging of the battery. The method of statistical geometry revealed the irregular nature of the packing of lithium atoms in the channel. Stresses in the channel walls arising during its maximum filling with lithium are significantly inferior to the tensile strength even in the presence of polyvacancies in doped silicene. The proposed design of the electrochemical cell is safe to operate. Copyright © 2020 American Chemical Society

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)

Molecular dynamics study of the stability of aluminium coatings on iron

Among the available protection systems for steel, the use of coatings is the most popular and economical method. One can protect the steel electrode from aggressive media with an aluminum coating. A thin Al film on an Fe substrate has been studied by the molecular dynamics method at a heating temperature from 300 K to 1500 K. A significant horizontal displacement of individual Al atoms on the edges of the film is observed during the simulation. The film begins to “spread” slightly near the edges. This “spreading” creates the conditions for the beginning of diffusion of iron atoms into aluminum. Some Al atoms were found to penetrate the Fe matrix at a temperature of 873 K. The total energy curve of the system shows both the melting transition in aluminum and phase transition from the body-centered cubic lattice to the face-centered cubic one at 1173 K. The binding energy for the Al atom in the lattice of the Fe crystal is smaller than that for Fe atoms. The calculated diffusion coefficients for Al and Fe have a significantly slower growth with a temperature in the range of 673 K ≤ T ≤1500 K. To describe the diffusion in a crystal using the molecular dynamics model, a temperature-dependent correction to the activation energy is calculated. The temperature dependence of the diffusion coefficient of aluminum atoms in an iron crystal can be represented as an Arrhenius expression with a temperature-dependent energy barrier for diffusion. © 2019, Institute for Metals Superplasticity Problems of Russian Academy of Sciences. All rights reserved