Raman spectroscopy and quantum chemical calculation on SmCl3-KCl-LiCl molten salt system

Abstract

The study on the ionic structure of SmCl3-KCl-LiCl molten systems is of guiding significance for the practical production of metal samarium and samarium alloys via Molten salt electrolysis (MSE) using this system as electrolyte. Based on density functional theory (DFT), the possible ionic groups in SmCl3-KCl-LiCl molten system were simulated by Gaussian and GaussView program and their theoretical Raman spectra were calculated. The calculated spectra were then compared with the experimental Raman spectra of molten 0.1–2 mol% SmCl3-(41 mol% KCl-59 mol% LiCl) to identify the ionic groups which might have existed. It is thought that SmCl4-, SmCl63-, Sm2Cl82- and Sm2Cl7- exist in the molten system. When the temperature is unchanged, the “lifetime” of SmCl63- is reduced while those of SmCl4-, Sm2Cl82- and Sm2Cl7- is increased with the increase of SmCl3 content. Within the temperature range of 773–809 K, when the content of SmCl3 remains unchanged, the “lifetime” of these complex ions decreases with the increase of temperature. Besides, the relative content of SmCl63- decreases with the increase of temperature. The wave function analysis of the four kinds of Sm-Cl ionic groups was also carried out using Multiwfn program. The net atomic charge of each ionic group, the direction of electron migration during the formation of the ionic groups, as well as the most prone to electrophilic and nuclear reactions of each ionic group, and the order of bond breaking during chemical reactions for the four groups were obtained.