The analytical approach has been developed in the framework of the continuous XY-model. This approach allows calculating the spontaneous magnetization reversal time of finite-length atomic chains on the metallic surface. The interaction of the magnetic moments of atoms is described by the classical Hamiltonian, which includes the Heisenberg exchange interaction, the Dzyaloshinskii–Moriya interaction, and the magnetic anisotropy energy. Using the Co/Pt(664) system as an example, it has been shown that the proposed method is in a good agreement with the results of the numerical simulation in the limit of short and long atomic chains. And for atomic chains of intermediate length, it can be used to estimate an upper bound on the spontaneous magnetization reversal time. We obtained the dependences of the spontaneous magnetization reversal time of finite-length Co chains the value of the exchange integral, parameters of the magnetic anisotropy, and also on the value of the projection of the Dzyaloshinskii vector onto the axis perpendicular to the plane containing the magnetic moments of the atoms. It is shown that the proposed method has a wide range of applicability both in terms of temperature and the values of the physical parameters characterizing the magnetic properties of the atomic chains.

The results of studying the effect of geometric and thermodynamic parameters of thermal evaporation and copper deposition on graphene lying on the Cu(111) surface on the adsorption of copper atoms, as well as their surface diffusion, are presented. The simulation was carried out by classical molecular dynamics using chains of Nose–Hoover thermostats. Interatomic interactions were determined by the Tersoff–Brenner, Rosato–Gillop–Legrand, and modified Morse potentials. A simple criterion for the thermalization of adatoms on graphene lying on a Cu(111) surface was formulated and tested. The average length and mean time of free path of a copper atom before and after thermalization at low (7 K) and room temperatures were studied for two evaporation temperatures. The probability of adsorption of a copper atom was found. The distributions along the directions of motion of adatoms during equilibrium diffusion were constructed. The distributions of the free path length and time were shown to have an exponential form. The influence of the Cu(111) substrate on the diffusion of the Cu atom on graphene was studied. The results obtained can be used to simulate the growth of copper nanoclusters on graphene by the kinetic Monte Carlo method.

The remagnetization mechanisms of finite-length ferromagnetic cobalt atomic chains at the Pt(664) surface have been investigated. It has been found that the remagnetization of short chains occurs due to the simultaneous flipping of all magnetic moments. At longer chain lengths, remagnetization occurs through the formation of a Néel-type anti-clockwise domain wall. The remagnetization of long chains can be achieved through both the formation of anti-clockwise and clockwise domain walls. The energy barriers for remagnetization of atomic chains with lengths ranging from 5 to 100 atoms have been calculated using the geodesic nudged elastic band method. In the framework of the harmonic approximation of the transition state theory, frequency prefactors have been calculated. A non-monotonic and sufficiently strong dependence of the frequency prefactors on both the chain length and an external magnetic field has been identified. The magnetization curves of Co atomic chains have been constructed, and the residual magnetization values and coercive force of the chains have been determined. The dependences of the coercive force on the chain length, temperature, and remagnetization rate of the magnetic field have been analyzed.

The energy barriers for magnetization reversal of the finite-size Fe chains on Pt(664) surface have been calculated using the geodesic nudged elastic band method. The Dzyaloshinskii–Moriya interaction and the dipole–dipole interaction have been taken into account. It has been found that the ground states of Fe/Pt(664) atomic chains are non-collinear at the ends. The magnetization reversal of short atomic chains occurs without the formation of the domain walls. While the magnetization reversal of the long atomic chains occurs via the formation of the domain walls. The interplay between the magnetic anisotropy energy and the Dzyaloshinskii–Moriya interaction leads to the rotation of the domain wall plane. As a result, the domain walls in Fe/Pt(664) atomic chains are intermediate configurations between Bloch and Néel walls. The dipole–dipole interaction weakly influences the value of the energy barriers and may be neglected. It is shown that the presented results can be explained in the framework of the classical continuous model. The constructed approximate functions correctly describe all features of the ground states and the saddle points. The structure of the domain walls and the dependencies of the energy barriers on the parameters of the model are different from the case of the Co/Pt(664) system investigated recently.

Equilibrium molecular structure of 3,4-dicyanofuroxan has been determined for the first time by means of gas electron diffraction (GED) and quantum chemical (QC) calculations. The GED values have been compared to those obtained from QC computations at different levels of theory. It has been discovered that the value of the O1-N2 bond is very sensitive to the QC method applied. The best fit to the experimental data has performed CCSD(T)/cc-pVTZ, whereas DFT methods applied in this work have been found to be less accurate. Peculiar features of 3,4-dicyanofuroxan molecular structure have been revealed by applying NBO, AIM and NCI analyses.

Energy barriers for magnetization reversal of the finite-size Co chains on Pt(664) surface are calculated with taking the Dzyaloshinskii-Moriya interaction into account. For the numerical calculations the geodesic nudged elastic band method is employed. It has been found that the ground states of such atomic chains are noncollinear. The magnetization reversal of short atomic chains occurs without the formation of domain walls. At the same time, there are two nonequivalent ways for the magnetization reversal of longer atomic chains. The first way is the formation of clockwise domain wall (CDW) and the second way is the formation of anticlockwise domain wall (ACDW). The second way is energetically preferable. It is shown that a metastable state corresponding to the location of ACDW in the middle of the atomic chain can appear. The variation of the parameters of the Hamiltonian shows that the magnetization reversal via the CDW formation can occur only in a certain region of the parameters. The influence of the long-range dipole-dipole interaction on the energy barriers for the magnetization reversal is also investigated. It is shown that the most of the presented results can be satisfactory explained in the framework of the XY-model. The magnetic configurations of the atomic chain near the local minima and the saddle points can be approximated with simple analytical functions.

The key characteristics of bearings used in the fuel and energy complex of the Russian Federation are considered, and proposals for the modernization of the Russian bearing industry to create bearings that meet modern requirements are satisfy the industry need for reliability, service life, operating conditions, etc., are presented. An analysis of the modernization of bearing plants in the Russian Federation is carried out, the economic and technical indicators that could be achieved as a result of the proposed measures are assessed.

In this letter, we use an analytical method for the estimation of magnetic properties of a wide range of ferromagnetic and antiferromagnetic single-atomic and biatomic chains.It is found that biatomic chains can be used as a bit of information at higher temperatures than temperatures for the same single-atomic chains. At the same time, the ratio between the spontaneous and induced remagnetization times is lower in the case of biatomic chains. According to our analysis, Co chains on a Rh(553) surface seem the most conducive to the creation of stable bits of information. The effects of nitriding the substrate or oxidation of the atomic chain are discussed. An analysis of magnetodynamic properties of ferromagnetic chains shows that the usage of atomic chains gives an opportunity to construct magnetic materials with a wide range of physical properties.

Two improved kMC models for investigations of the magnetic properties of finite-size atomic chains are presented. These models take the possible noncollinearity of magnetic moments into account. The spontaneous remagnetization of ferromagnetic Co chains on Pt(997) surface and antiferromagnetic Fe chains on Cu_2N/Cu(001) surface is investigated in the framework of our models. The results are compared with the results of the simple kMC model. It is also shown that a single domain-wall approximation can be successfully used to estimation of the reversal time of the magnetization. Therefore, the improved kMC models can be used for analytical calculations as well as for computer simulations.

The formation of CoCu and PtCu alloys on the stepped Cu(111) substrate was simulated. Dendritic and finger-like protrusions grow near the edges of the steps. The shape and the internal structure of the protrusions depend on the type of the step edge, temperature and concentrations of impurity atoms. The internal structure and the shape of the protrusions are significantly different in PtCu and CoCu alloys. Pt atoms tend to be surrounded by Cu atoms and Co atoms tend to combine into Co backbones. The dendritic protrusions usually grow at 200 K and the finger-like protrusions usually grow at 300 K. The shape of the protrusions also depends on the type of the step edge and the concentration of impurity atoms. The main differences of PtCu and CoCu protrusions can be explained by the values of the diffusion barriers of the key processes.

The magnetization reversal of atomic chains on metal surfaces has been theoretically studied using the analytical method developed earlier and the geodesic nudged elastic band method. The atomic chains can be divided into the following three types: chains with a small, intermediate, and large domain wall width. A dipole–dipole interaction is shown to cause an increase in the average spontaneous magnetization reversal time of FM|| and AFM⊥ chains and a decrease in the magnetization reversal time of FM⊥ and AFM|| chains. For FM⊥ and AFM⊥ chains with a medium-width domain wall, taking into account a dipole–dipole interaction leads to the appearance of an energy barrier between two states of a domain wall differing in the direction of rotation of magnetic moments. The magnetization reversal of atomic chains from the third type can occur in the following two ways: all magnetic moments are reversed either simultaneously or one by one. The transition from one magnetization reversal mode to another occurs at a critical length N 0 . The effect of a dipole–dipole interaction is most significant when the chain length is close to N 0 . Numerical estimations have shown that taking into account a dipole–dipole interaction can change the magnetization reversal time of a chain by an order of magnitude in some cases.

The formation of Pt/Cu clusters on a stepped Cu(111) surface has been theoretically investigated using the self-learning kinetic Monte Carlo method. It has been shown that by varying Pt/Cu cluster growth conditions, one can prepare different nanostructures, such as spatially extended and branching dendrites and fingers of different geometry. It has been found that the shape of clusters depends mainly on three parameters: temperature, platinum relative concentration, and the type of step on which the cluster grows. Dendrites grow under the following conditions: the temperature in the system must be no higher than 200 K, and the system must contain platinum atoms. Depending on the type of step, either dendrites extended normally to the step or branching dendrites arise. At room temperature, fingers grow on steps, the length of fingers also being dependent on the type of step. Different shapes of clusters on different steps arise from the anisotropic diffusion of atoms near the corners of clusters, which can be explained by taking into account energy barriers for atom hops over the Cu(111) surface.

The formation of nanocontacts during the indentation of a scanning tunneling microscope (STM) tip into a Pt/Cu surface alloy has been studied by the molecular dynamics method. It has been established that the Pt atoms move in the copper nanocontact through jumps over atomic layers in the direction from the copper surface to the base of the STM tip, while the Cu atoms move in the opposite direction. The formation of nanocontacts for various orientations of the STM tip, a temperature from 300 to 800 K, and various numbers of Pt atoms immediately beneath the STM tip has been studied. It is shown that the probability of the formation of a mixed Pt–Cu nanocontact can reach 50%.

We discuss the current state of a promising area of modern physics, the study of the physical properties of metal nanowires and atomic chains. One-dimensional nanostructures are attractive because of both the promise of their practical applications and the possibility of using them to test various theoretical models and approaches by comparing theoretical results with experimental data. We describe experimental conditions under which metal nanowires form on metal and semiconductor surfaces. We give special attention to theoretical models describing the scenario of nanowire growth on various surfaces. We analyze the main experimentally determined factors that affect the distribution of nanowire lengths. We show that the distribution of nanowire lengths on metal and semiconductor surfaces depends not only on external parameters but also on the formation time. We consider the magnetic properties of finite-length atomic chains located on the surfaces of metal and semiconductor crystals. We demonstrate a correlation among the structural, electronic, and magnetic properties of nanowires. We elucidate the effect that nanowires exert on the electronic properties of the surface on which they form. The nature of edge states is explained. The electron states of nanowire atoms are shown to be sensitive to the nanowire length. We discuss the Rashba effect for metal nanowires on a semiconductor surface and analyze how the exchange energy between atoms and the magnetic anisotropy energy affect the macroscopic characteristics of nanowires, such as their critical temperature and the time of spontaneous magnetization reversal.

Formation of embedded Co nanostructures in Cu(001) surface under electromigration is investigated on the atomic scale by performing self-learning kinetic Monte Carlo (kMC) simulations. The analysis of simulation results reveals the following important result. The electromigration of vacancies does not influence on the self-organization of Co nanostructures in the first layer of Cu(001) surface at all values of current density, which can be achieved in experiments.

In this paper, we propose a new theoretical approach that combines classical MD method and a one-dimensional diffusion model. We have shown that our approach allows to extrapolate the results of MD simulations to the experimental timescale. As an example, the formation of Cu–Pt nanocontacts in the STM-BJ experiments was investigated. STM-BJ simulations with copper STM tips and Cu–Pt surface alloys were performed in a wide range of temperatures (300–900 K), number of Pt atoms in the substrate (1–7) and for different orientations ((100), (110) and (111)) of the STM tip. Using our approach, we predicted that it is possible to use the STM-BJ technique to prepare Cu–Pt nanocontacts. The presented approach should work well in all cases when the diffusion of atoms occurs via interlayer jumps.

The formation of nanocontacts consisting of copper (Cu) and platinum (Pt) atoms at various temperatures (0–300 K), relative concentrations of platinum atoms (0–20%), and elongation directions [100], [110], and [111] is investigated using molecular dynamics method. The nanocontact breaking area has a complex amorphous structure, for the description of which we propose three models. To determine the quantitative contributions from these models to the structure of the breaking area, we analyze the short-range order using the radial distribution function. The temperature dependence of the nanocontact structure in the breaking area is analyzed.

The formation of the Cu-Pt nanocontacts has been investigated by means of classical molecular dynamics simulations. The simulations of the mechanically controlled break junction experiment have been performed in wide ranges of temperatures (0-300 K) and at relative Pt concentrations (0-20%). The structure of the breaking area has been studied 2 ns before the final breaking of the nanocontacts. The length of the breaking area increases with the increase of the temperature and decreases with the increase of the relative Pt concentration. The structure of the breaking area has been investigated by means of the radial distribution function method. The breaking area usually has one of the following structures: (i) a bulk-like structure, (ii) a structure consisting of centered icosahedrons rotated 90°, or (iii) an icosahedral structure composed of pentagonal rings. The structure of the breaking area is almost independent of the temperature and the stretching direction due to the strong Cu-Pt interaction.

A new carbon–copper interaction potential is proposed to simulate the moiré structure of graphene on the copper surface. It is shown that the resulting moiré structure is in qualitative agreement with scanning tunneling microscopy images. The thickness of the moiré structure and the binding energy of graphene with the surface agree within the error with the existing experimental data. The proposed potential can also be used to simulate the diffusion of copper atoms over the graphene surface. The diffusion of an atom and a copper dimer in a wide temperature range is studied. It is found that the contribution of the vibrational free energy of copper atoms should be taken into account when simulating diffusion.