[en] The atomic structures of liquid rubidium were simulated by classical and first-principle Molecular Dynamics methods for a range of temperatures. The pair potentials necessary for the Classical Molecular Dynamics calculations were obtained using diffraction data by the Schommers iterative method. In all cases simulated pair correlation functions and structure factors correctly reproduced the experimental ones. A Delaunay simplex, comprised by four atoms, is the simplest element of the structure. All atomic aggregates in an atomic structure consist of them. The structure factor of the simplicial voids system is additional structural characteristic which allows seeing distinction in structures with almost similar pair correlation functions

[en] The standard magnetic model in the current CALPHAD modelling is based on the Inden–Hillert–Jarl model and can be used to ferromagnetic and antiferromagnetic alloys. In this work, we demonstrate that this model can also be applied to alloys with more complicated forms of magnetism. The concept of ‘effective magnetic moment’ has been introduced as a measure of the maximum magnetic entropy. To calculate this quantity, it is necessary to know the local magnetic moments on the atoms of the components. A case study on the Fe –Cr system has been performed by Density Functional Theory (DFT) formalism at 0 K. It is shown that the CALPHAD modelling using the concept of effective magnetic moment leads to good agreement with the data of ab-initio modeling of the magnetic contribution to the mixing energy of Fe-Cr alloys. (paper)

[en] The equilibrium structure and the properties of ternary Fe–X–C (X = Si, P, S, Cr, Mn) systems are studied by ab initio simulation using the WIEN2k software package. The calculations are performed by the full-potential linearized augmented plane wave method (FLAPW) with allowance for the generalized gradient approximation (PBE-GGA). These methods are most accurate in terms of the density functional theory. The magnetic structure of Fe–X–C alloys and the interaction between carbon and impurity atoms at various distances are analyzed. Repulsion is detected between impurity silicon, phosphorus, and chromium atoms and carbon atoms in all three coordination shells, which significantly increases the dissolution energies of these impurities. Analogous repulsion for the first two coordination shells is also observed for the interaction of sulfur and carbon atoms, and weak attraction between these atoms appears in the third coordination shell. The interaction of carbon with manganese is characterized by attraction in the first two coordination shells, and the dissolution energies of both manganese and carbon decrease.

[en] The results of computer simulation of the influence of silicon impurities on the degree of tetragonality and on the interaction of carbon atoms in the body-centered cubic (BCC) lattice of iron by the molecular-dynamics method are reported. The influence of silicon on the martensite-lattice parameters has been established, as well as the dependence of the deformation interaction parameter λ₀ determining the critical temperature of the BCC–BCT (body-centered tetragonal) transition on the silicon concentration, is calculated on the basis of the Zener–Khachaturyan theory of ordering. It is found that the λ₀ parameter decreases by 18% from 5.2 to 4.2 eV/atom upon an increase in the silicon content up to 10 at %.

[en] A modification of the LMTO method was used for the investigation of the electronic structure of melts in the wide temperature and density range. Modelling consisted of two steps: self-consistent calculation for a supercell (approximately 50 atoms) by LMTO method, and calculation of electronic structure and properties of a large system (approximately 4000 atoms) by recursion method with LMTO basis functions. This method was tested on Fe, Cs and Hg melts. Our results are in agreement with the ab-initio calculation results for temperatures near the melting point. Features of metal-nonmetal transition for Hg and Cs at high temperatures were obtained

[en] We calculated the temperature dependences of electroconductivity for the different metals, such as alkalis (caesium), transition metals (iron), and mercury by Kubo-Greenwood formula. Atomic models of 1000-4000 atoms were obtained by Shommers method using the data of diffractional experiments for the wide temperature range. The electronic structure and interaction parameters for supercells of 30-50 atoms were got by LMTO method. The recursion method was used for the calculation of DOS and diffusivity quotients. The lowering of the DOS at the Fermi level was carefully examined. The results obtained are in good agreement with other authors' in views on the nature of the metal-nonmetal transition in different liquid metals. The calculated DOS and conductivity for all metals match the experimental data well

[en] An approach to complex modeling and control of atmospheric mass transfer of radioactive contamination is proposed. (author)

[en] This article presents the results of a study on the activity of natural radionuclides in the soils of the southern part of the Kurama Range. It was found that the activity of radionuclides in the soil is related to the landscapes of the area and the migration of elements from them. (author)

[en] The paper presents ab initio simulation with the WIEN2k software package of the equilibrium structure and properties of silicon and carbon atoms dissolved in iron with the body-centered cubic crystal system of the lattice. Silicon and carbon atoms manifest a repulsive interaction in the first two nearest neighbors, in the second neighbor the repulsion being stronger than in the first. In the third and next-nearest neighbors a very weak repulsive interaction occurs and tends to zero with increasing distance between atoms. Silicon and carbon dissolution reduces the magnetic moment of iron atoms.

[en] Mobile hydrogen, when dissolving in metals, redistributes due to the density gradients and elastic stresses, and enables destruction processes or phase transformations in local volumes of a solvent metal. It is rather important in solid state physics to investigate these interactions. The first-principle calculations performed in terms of the density functional theory, are used for thermodynamic simulation of the elastic stress effect on the energy of hydrogen dissolution in α-Fe crystal lattice. The paper presents investigations of the total energy of Fe–H system depending on the lattice parameter. As a result, the relation is obtained between the hydrogen dissolution energy and stress. A good agreement is shown between the existing data and simulation results. The extended equation is suggested for the chemical potential of hydrogen atom in iron within the local stress field. Two parameters affecting the hydrogen distribution are compared, namely local stress and phase transformations.