A. E. Galashev

Compaction of a copper film on graphene by argon-beam bombardment: Computer experiment

The process of Cu-film compaction on graphene under the action of Ar13 clusters hitting the surface with an energy of 5 eV is studied using the molecular-dynamics method. The horizontal and vertical components of the self-diffusion coefficient of a Cu film and graphene, the stresses on the horizontal Cu area, the Cu-graphene interaction energy, the radial distribution function of the film, and the graphene surface roughness under bombardment of a target by Ar13 clusters are calculated. Graphene exhibits some pliability, and traces of Cu film surface relief remain on it after total exposure under the impacts of Ar13 clusters.

Molecular dynamics simulation of the physicochemical properties of silicon nanoparticles containing 73 atoms

The physicochemical properties of 73-atom silicon nanoparticles that have a crystal structure, a random atomic packing, and a packing formed by inserting a 13-atom icosahedron into a 60-atom fullerene are investigated using the molecular dynamics method. Analysis of the behavior of the internal energy, the radial distribution function, the distribution of bond angles, and the specific heat at a constant pressure Cp in the temperature range 10–1710 K indicates that a crystalline nanoparticle undergoes melting at a temperature of 710 K and that the structural transformations occurring in particles with an irregular atomic packing exhibit specific features. It is demonstrated that the temperature dependence of the self-diffusion coefficient follows a linear behavior. Local deviations from the linear behavior are most pronounced for the crystalline nanoparticle.

The stability and structure of (N2)j(H2O)i and (Ar)j(H2O)i clusters

The stability and structure of water clusters absorbing nitrogen molecules or argon atoms was analyzed by molecular dynamics simulation at 233 K. The (∂μ/∂i)V, T derivative of the chemical potential, a value characterizing the stability of a cluster with respect to its size, depends linearly on the number of molecules i. According to this criterion, the clusters under study become stable near i = 40. The average length of H-bonds increases monotonically in the growing cluster of pure water and exhibits oscillatory behavior if the growing cluster contains N2 molecules or Ar atoms. The number of H-bonds per molecule oscillates between one and six as the cluster size changes. These oscillations are damped in pure water and sustained for clusters containing impurities, especially argon.

Computational study of interaction of bromine ions with clusters (O2)6(H2O)50 and (O3)6(H2O)50

Interaction of bromine ions with water clusters that have absorbed the molecules of oxygen and ozone is studied using a molecular-dynamics simulation of flexible molecules. The cases of location of Br− ions on the surface and in the bulk of the cluster are described. Water clusters with ozone molecules remain stable during their interaction with the Br− ions, while oxygen molecules are found to evaporate from the cluster when Br− ions appear in its bulk. In the presence of Br− ions, the infrared spectra of systems with O3 molecules are observed to be intensified. The intensities of the IR spectra with O2 molecules may both increase and decrease depending on the arrangement of the Br− ions. The Raman spectra are sensitive to the appearance of Br− ions only for systems that contain oxygen molecules. As a result of interaction with the Br− ions, the power of IR radiation emitted by the clusters can not only increase, but also decrease.

Computer simulation of Li+ ion interaction with a graphene sheet

The behavior of lithium ion in a flat channel formed by graphene sheets under the effect of an electrostatic field is studied by means of molecular dynamics. The optimum size of the gap between the sheets of graphene in which the movement of ions occurs with minimal deviation from the directions given by the field is found. The horizontal and vertical mobility of carbon atoms in each of the graphene sheets between which a lithium ion moves are calculated along with the stress tensor of the graphene channel, the σzz-component of which is most critical during the motion of the ion within the channel.

Computer analysis of the stability of copper films on graphene

The stability of copper films of three types on graphene was studied by the molecular dynamics method. Films in the form of (111) and (100) planes and elongated (111) plane of the Cu crystal were considered. The initial arrangement of the Cu atoms relative to the carbon atoms was shown to considerably affect the thermal stability of the films. The most stable film was the one formed by placing Cu atoms in the nonadjacent hexagonal cells of graphene. The horizontal mobility of Cu atoms in this film decreased, while the vertical mobility increased as the temperature increased. The most significant stresses in this film were determined by the zigzag and chair orientations of the graphene sheet.

Molecular-dynamic modeling of the spectral characteristics of the ozone-water cluster system

The absorption of one to six ozone molecules by the (H2O)25 cluster is studied by the method of molecular dynamics under near-atmospheric conditions. The capture of O3 molecules by a water cluster produces a decrease in the integral intensity of IR absorption, reflection, and Raman spectra. IR absorption spectra are highly sensitive to the number of ozone molecules absorbed by a water cluster. The observed photon emission time and the radiation intensity of a dispersed aqueous system with absorbed ozone molecules are appreciably reduced relative to the analogous characteristics of a pure water cluster system.

Computer simulation of the thermal stability of nickel films on two-layer graphene

The structure and the dynamic and mechanical properties of monolayer nickel films deposited on two-layer graphene are studied in the temperature range 300 < T < 3300 K by the molecular-dynamics method. A part of the Ni atoms remains on the graphene sheet even at T = 3300 K for both one- and two-sided coatings. The radial distribution functions of the upper and lower metal films differ significantly even at T = 300 K. The temperature dependence of the horizontal and vertical components of the self-diffusion coefficient of a one-sided nickel film exhibits a jump above 1800 K. No similar specific feature was observed for a two-sided coating of graphene with this film. The stress components acting in the nickel-film plane disappear with an increase in temperature for a shorter time in the case of one-sided coating.

Numerical simulation of heating an aluminum film on two-layer graphene

The behavior of a monolayer aluminum film on two-layer graphene upon heating from 300 to 3300 K was studied by the molecular dynamics method. A stretched film is nonuniformly contracted with an increase in temperature. Aluminum atoms remain on graphene even at 3300 K. Heating reduces stresses in the film plane. Upon heating to 3000 K, the long-range order in graphene is transformed into the mid-range one. The increase in the intensity of vertical displacements of C atoms in one graphene sheet (caused by an increase in temperature) generally reduces the corresponding intensity in the other sheet, whereas the horizontal components of mobility, with few exceptions, behave similarly. Upon heating, stresses in the upper graphene sheet decrease with different rates for different directions.

Computer Study of Physical Properties of Silicon Nanostructures

The method of molecular dynamics is applied to the study of variations in the physical properties of vitreous and amorphous silicon nanoparticles when heated from 300 to 1700 K. The nanoparticles consist of 300, 400, and 500 atoms. The energy and the average length of the Si-Si bond are calculated, and the average number of bonds per atom is determined. Thermally induced strains tend to change the distribution of the excess potential energy among the concentric layers in the nanoparticles. It is shown that, energetically, the most preferential layer is the middle spherical layer of the “warm” nanoparticle. The temperature behavior of the radial and tangential components of the atomic mobility coefficient in the concentric layers is considered. It is established that there is a liquid layer at the nanoparticle surface in the vicinity of the transition to melting. The vitrified Sin nanoparticles are kinetically more stable than the similar-sized amorphous particles.