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