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

Processing of fast neutron reactor fuel by electrorefining: Thematic overview

This work provides basic knowledge on the spent fuel management on the basis of the published literature data on electrorefining. This review examines three main areas of work devoted to electrorefining. These are electrodeposition and electrodissolution using solid and liquid electrodes, as well as mass transfer in phases present during electrorefining. As part of this research, the composition of the irradiated metallic fuel was estimated. Due to the great potential difference between solid cathodes, it is possible to separate actinides from lanthanides. The co-deposition of metallic Pu and U in the eutectic LiCl-KCl melt containing UCl3 and PuCl3 indicates stable co-precipitation of U and Pu at U3+ concentration less than ~0.2 wt. Periodically performed electrical transport of ions to liquid (Cd) and solid cathodes in the galvanic mode made it possible to deposit preferentially U on the solid cathode, and Pu and Am on the liquid cathode. Oxidation of these metals caused fluctuations in the anode potential. The electrode processing after electrorefining is investigated. This process consists of oxidizing the actinides remaining in the liquid electrode by adding CdCl2 and removing the associated chloride by high-temperature distillation. During the electrorefining of irradiated metallic fuel, the fission products accumulate in the molten salt. Reduction of uranium on a solid cathode from a spent molten salt using a liquid Cd-Li anode is considered. A model that describes electrorefining with a liquid metal anode, solid cathode, and molten LiCl-KCl salts, is presented. The formation of plutonium at the surface of a solid cathode is analyzed. In a one-dimensional model of an electrorefiner, it is shown that the concentration of Pu at the cathode cannot be predicted from the Cm concentration in the melt. © 2020 John Wiley & Sons LtdState Atomic Energy Corporation ROSATOM, ROSATOM, (17706413348200000540)This work was supported by the State Atomic Energy Corporation Rosatom (State Contract No. Н.4о.241.19.20.1048 dated April 17, 2020, identifier 17706413348200000540)

Recovery of actinides and fission products from spent nuclear fuel via electrolytic reduction: Thematic overview

Spent nuclear fuel (SNF) from modern light water or thermal reactors containing uranium oxide with small concentrations of plutonium and other actinide oxides is converted into metal by the electrolytic reduction. The obtained metal must be subjected to further processing (electrorefining). This review reflects the achievements in development SNF electrolytic processing, concepts of the technological operations, and a model describing the electrochemical process. The technological scheme for the electrochemical reduction of SNF and MOX fuel is considered. The complexity of a carbon anode application in the process of UO2 electrolytic reduction is reflected. The reduction processes of alkali, alkaline earth (AE), and rare earth metal oxides as well as oxide compounds of zirconium are demonstrated. The reduction of lanthanum oxide and oxy-chloride to the metallic form by adding metallic nickel to the molten salt is discussed. The solubility of Li2O in molten salts is interpreted depending on the amount of dissolved alkali and AE metal chlorides. The considered pyroprocessing technology enables a much greater release of the energy accumulated in uranium ore, and recycling all actinides allows reducing significantly the amount of nuclear waste and the time it must be isolated. © 2021 John Wiley & Sons Ltd.State Atomic Energy Corporation ROSATOM, ROSATOMThis work was supported by the State Atomic Energy Corporation Rosatom (Government agreement number H.4o.241.19.21.1070 dated 16 April 2021 «Development of the technology and facility for the pyrochemical reprocessing of the spent nuclear fuel of the fast neutron reactors. 2021 stage»)