First-principle investigation of the structure and vibrational spectra of the local structures in LiF–BeF2 Molten Salts

Abstract

In this article, the identified local structures are investigated using Density Functional theory to reveal the effects of the interaction on the geometry and vibrational dynamics of the ternary-system. Ab initio molecular dynamics simulation is used to simulate the identified clusters in gas phase and the salts in condensed phase. Vibrational spectra are computed either through normal mode analysis or Fourier transform of the autocorrelation function of the total dipole moment. We find that two of the most intense bands can be taken as the signature of formation of the local structures (BeF42−, Be2F73−, and Be3F104−). The signature bands are found in the correspondent region in the spectra of the salts, indicating the existence of the local structures. Vibrational density of states spectra found that the feature frequency of Li atoms is as low as 400cm−1, suggesting it is not tightly bound to other species. Current study sheds some light into understanding of the interaction and dynamics of the molten salt.