I. A. Babinа, B. S. Vorontsov, V. V. Moskvin, A. O. Babin. 

ABSTRACT

       Fluoride salt melts are used in many metallurgical processes and technologies. It is known that even very small additions of REM (rare earth metals) significantly change their structurally sensitive properties. Possible mechanisms of such influence and different models of REM ion participation in the structure formation of fluoride melts are discussed. The possibility of the formation of LnF₆Me₁₄ complexes (Ln = La, Ce, Pr, Nd, Sm, Eu; Me= Li, Na, K, Cs,) by REM (rare earth metal) ions in fluoride salt melts has been confirmed by the methods of molecular mechanics and quantum chemistry. Such a composition is postulated in the literature on the basis of the interpretation of spectral data and the hypothesis of the proximity of the structures of fluoride salts in the liquid and solid states at high temperatures. The calculated data on the geometric structure of molecular models of such complexes in the region of the minima of the potential energy surface are presented. Three types of structures with different geometric structures have been identified. The possibility of forming a self-consistent electronic subsystem in models with optimized geometry is shown. The features of the density of electronic states in the valence and SPARKLE approximations are analyzed. It is shown that the electronic levels of the alkali metal atoms coordinated by REM ions significantly affect the density of the electronic states of the base of the complex, which indicates the prospects of the obtained models for further investigation of the spectral properties. The constructed models are promising for subsequent calculations of spectral characteristics. Molecular models of complexes are shown, the formation of which is postulated by the introduction of ions of rare-earth elements of the lanthanum group into salt fluoride melts. Their geometric characteristics for the states corresponding to the minima of the potential energy surface are determined by the method of molecular mechanics with the MM+ force field. The development of an alternative approach, which begins with the construction of molecular models of complexes based on REM and is covered by the calculation of various spectral characteristics associated with the electronic structure and geometry of these complexes.

KEY WORDS:

molecular model complexes, a model experiment, the molten fluoride ions, the spectral characteristics of the electronic structure

DOI: 10.31857/S0235010621040022

V. G. Postovalov, V. P. Kondratiev, E. P. Romanov

ABSTRACT

The theory of atomic transfer in liquid 3d-transition metals has been developed in the present article to predict their self-diffusion and viscosity coefficients. It is shown, that the theoretical values of these coefficients are in good agreement with the experimental data. It was discovered that liquid chromium, manganese, iron, cobalt and nickel shows anomalies of transport properties. Self-diffusion coefficients of liquid scandium, titanium, vanadium

and chromium are predicted in a wide temperature range.

KEYWORDS

liquid 3d-transition metal, self-diffusion, viscosity

DOI: 10.1134/S0235010619030083

D. N. Kamaev

ABSTRACT Modelling of the phase equilibriums in the system BeO–Al2O3 has been carried out with using regular, subregular theories and Redlich–Kister polynomials. Calculation with using subregular theory and Redlich–Kister polynomials correspond to the experimental data.

KEYWORDS

diagram, thermodynamic modeling, beryllium oxide, aluminum oxide

DOI: 10.1134/S0235010619030071

Yu. Ya. Gafner, S. L. Gafner, L. V. Redel

ABSTRACT

Currently, silver, including nanostructured, is widely used in many industries due to its unique heat and electrical conductivity, as well as strong catalytic activity. One of the new applications of silver nanoparticles is their use in plasmon applications, which are determined by the strong interaction between the electromagnetic wave and free electrons in nanostructures. Particles of a metal with a size smaller than the wavelengths of visible light can strongly absorb light due to the phenomenon of surface plasmon resonance, due to the collective oscillation of conduction electrons. The frequency and intensity of the plasmon resonance depends on the distribution of the polarization charge in the nanostructure, which, in turn, is determined by the shape and structure of the nanoparticle. Thus, control of the structure of the metallic nanostructure allows you to control the wavelengths of light that it dissipates and absorbs. Based on this, the boundaries of the thermal stability of the initial fcc phase in silver clusters up to 2.0 nm in size were investigated using the molecular dynamics method using the modified TBESMA potential. It is shown that at a silver nanoparticle size of more than 200 atoms, fcc cluster structure is thermally stable up to the melting point. For silver nanoparticles of smaller dimensions, numerous cases of a thermally induced change in the cluster structure were observed. Thus, for the application of small silver clusters in plasmon applications, it is necessary to take into account the thermal stability of their cluster structure.

KEYWORDS

nanoclusters, Ag, structure, computer simulation, tight binding

DOI: 10.1134/S0235010619030058