Section of Theory and computer simulations in materials science and condensed matter physics

Adsorption of lithium on a carbon nanotube with a vacancy defect.

It was found by molecular dynamics that the deposition of hydrogenated and dehydrogenated carbon atoms on defect-free graphene depends on the degree of hydrogenation of carbon atoms.

Molecular dynamics simulation is utilized to analyze the role of applied compressive and shear strain on the mechanical performances of Al/Ti composite. Mixing of atoms near the interface between Al and Ti during deformation is analysed.

Steady state isotropic optimal superplastic deformation in 175 materials systems of different classes studied can be represented by the equation 8 in the main text

Distribution of the third main deformation the hemispherical shell from a conical blank

Values of Lankford coefficients for various thickness reduction at rolling UFG steel.

A theoretical study of the structure and properties of a chiral SA3 diamond polymorph has been performed. The chiral SA3 phase can be obtained by polymerization of nanotubes (5,4). The unambiguous identification of this phase is possible using X-ray diffraction analysis, X-ray absorption and Raman spectroscopy.

Athermal grain boundary sliding due to the motion of virtual dislocations of planar shear mesodefect essentially facilitates microcracks nucleation.

Self-diffusion parameters for melts of Ni-Al and Ti-Al systems, depending on the concentration of the components, have found by the method of molecular dynamics

Quantum theory and analysis of chemical reactivity were applied to choose suitable adsorbents that ensure efficient solid-phase microextraction of dioxane and dioxalane from milk. It is shown that carbon nanostructures possess some advantages over primary and secondary amines.

Method for determining energetically favorable landing sites of carboxyl groups during functionalization of graphene nanomesh by atomic charge distribution

The process of formation of a solitary wave under external harmonic action at the frequencies of the forbidden zone of the crystal.

A defective nanotube containing 5 and 8 -membered rings shows the highest adsorption capacity of 1.82 %wt/wt which is higher than the pristine nanotube and the adsorption capacity increases with %defect.

Modification of a microstructural model allows describing the strain variation on isothermal holding and predicting conditions (temperature and stress), at which the maximum of isothermal strain is attained.

Computer modeling of the pressure welding process of cylindrical workpieces from heterophase nickel-based superalloys through an interlayer was carried out.Two combinations of materials to be welded were considered: I – cylinders of the same wrought EP975 nickel-based superalloys in the initial coarse-grained state were welded through an interlayer of EP975 with a fine-grained microstructure; II – cylinders of different kinds nickel-based alloys, including wrought alloy EP975 in a coarse-grained state and intermetallic alloy VKNA-25 with a single-crystal structure, were welded through an interlayer of EP975 alloy with a fine-grained microstructure of the microduplex type. The distribution of equivalent, axial, radial, circumferential and shear components of stress and strain in the samples have been investigated. Analysis of the simulation results allows us to conclude that, in comparison to welding of the same name materials, when welding of different kinds materials, the radial, axial and circumferential stresses values increase. The maximum values area of shear stresses in the region of contact between the cylinders and the interlayer also increases. This factors combination allows us to conclude about more favorable pressure welding conditions for welding of different kinds alloys in comparison with the same name materials.

The dependence of the melting temperature of Ti and TiAl nanoparticles on their diameter in vacuum and in Al matrix is studied by the method of molecular dynamics

The resulting model of the hysteresis loop provides a sufficiently high-quality approximation of the values of magnetic induction with an error not exceeding the measurement error, and its application doesn't require complex calculations or the development of a special computer program.

Displacement of the ferromagnetic film hysteresis loop when the system is heated.

In this work, models of a monolayer of pyrolyzed polyacrylonitrile containing pairs of metal atoms have been created. A complete optimization of the cluster geometry was carried out using the DFT method.

Spatially localized breather excitations are investigated for the model of a discrete Heisenberg spin chain, which includes an antisymmetric exchange interaction and single-ion anisotropy of the easy-plane type. Taking into account the antisymmetric exchange leads to the excitation of only antisymmetric magnetic discrete breathers.

Investigation of deformation heating during ECAP using the Deform-3D complex for mathematical modeling.

Schematic representation of boron nitride composed of nitrogen (red) and boron (blue) atoms.

The dependences of the critical value of the disclinations dipole strength on the mesodefect length obtained at various values of the strength of the planar mesodefect are shown. The regions of parameters for which stable cracks can exist for each of the given values of the strength of the planar mesodefect lie above the corresponding curves.

Based on the obtained experimental data a physically motivated model is formulated for the ferritic transformation with allowance for the effects of deformation and concurrent recovery of austenite. The model is first to evaluate variation of nucleation barriers owing to the hydrostatic component of internal stresses at austenite grain boundaries.

Schematic of the magnetic pulse installation for tensile testing.

Illustration of the temperature dependence of the activation threshold for desorption at low levels of surface filling with deposited atoms: the presence of two curves indicates a rearrangement of the surface structure.

Zero misorientation interfaces (ZMIs) in graphene and their disclination schemes. Minimum disclination strength is ω = π/3.

Structure formation of diamond-like bilayers.

The transition from a direct to an inverse Hall-Petch dependence for nanocrystalline ceramics is related to an increase in the number density of triple junctions and dislocation emission from these junctions.

Despite different atomic structures and degrees of symmetry of bcc and hcp crystals, the topological aspects of the processes of growth and shrinkage of {112}bcc and {10-12}hcp deformation twins are equivalent.

The features and migration mechanism of tilt boundaries with the misorientation axis <110> in an fcc crystal using nickel as an example are studied by the method of molecular dynamics

Energy spectrum of the main elements in the material: a) electrodes (technical copper); b) particles of sediment powder containing zinc (particle 2 in Table 1)

The functional and mechanical properties of porous shape memory alloys are determined by the phase transformations and the features of the pore structure. The modeling results aimed at clarifying the influence of these factors on the behavior of porous NiTi.

The group-theoretical classification of atomic vibrations in molecular and crystal structures is discussed. Wigner’s classification, which is valid for small-amplitude oscillations, is generalized to the case of oscillations with arbitrary amplitudes. An elementary introduction to the theory of bushes of nonlinear normal modes is given.

The conditions for the appearance of a circular current during the ordered motion of the C60 fullerene on graphene with a defect in the form of local hydrogenation of the atomic network are found. The defect should form a bowl-shaped well in the energy surface of interaction of C60 with graphene, along the edges of which the fullerene will make a circular motion.

Pressure-strain curves for Ni-graphene systems under hydrostatic tension at 0 K and corresponding snapshots of composite at different strain. Ni atoms are shown by blue and C atoms are shown by red.

The new hybrid nanostructures formed by graphene sheet and C60-fullerene fragment were studied using density functional theory

The approach based on the theory of bent beams allows describing the deformation behavior of porous NiTi with non-ordered structure of pore channels.

A stress-strain state computer simulation of samples imitating bimetallic «disk-shaft» type parts for a gas turbine engine from dissimilar heat-resistant nickel-based superalloys during pressure welding with a shear was carried out. Two shaft motion schemes were considered: the shaft into the disk introduction, and the combination of the introduction and rotation of the shaft. It has been established that to obtain solid phase joint between the shaft and the disk, it is preferred to use pressure welding when the introduction and rotation of the shaft.

Percolation effects are considered in the model of a one-dimensional Ising magnet of finite nanometer size with boundary conditions - dangling ends.

Dependence of magnetization magnetic field for films on temperature

Relative intensities of UV-Vis spectra of silicon biprismanes strongly depend on doping. In particular, doping with methyl radicals and fluorine atoms provides prevalent adsorption intensities of octagonal and hexagonal biprismanes, respectively.

The formation of free volume in grain boundaries and triple junctions during crystallization using nickel as an example is studied by the molecular dynamics method

It is shown that the collective effects of the influence of the presence of thin magnetic layers (with a reduced value of the magnetic anisotropy constant) in a five-layer ferromagnet on the dynamics of domain walls is preserved at the action of an external magnetic field, whereas when a DW moves along inertia almost completely disappear. Chart of possible scenarios of DW dynamics depending on its initial velocity and the distance between two thin layers.

When fluorinating 4-6-12 graphene layers two stable polymorphic varieties of fluorographene layers T1- or T3-type can be formed

The Letter presents a detailed analysis of the isomerization and decomposition mechanisms of silabiprismanes. Their thermokinetic parameters in the Arrhenius law are determined, and estimations of their lifetimes at various temperatures are given.

An original algorithm for constructing full-atomic models of X- and T-shaped seamless junctions between single-walled carbon nanotubes of various chiralities is proposed and its software implementation in the SeamMaker package is implemented.

Model potential for evaluating the transparency coefficient during tunneling of an electron with energy E through the Coulomb barrier of the target electron (r0 ~ 10-15 m, r1 >> r0)

The spin wave spectrum of the bilayer case for a strong value magnetoelectric interaction between magnetic and ferroelectric layers

New one-dimensional discrete breathers are excited in a close-packed atomic row of 2D Lennard-Jones triangular lattice, using the one- and two-component delocalized nonlinear vibrational modes of one-dimensional lattice reported by Chechin et al.