PUBLICATION: JOURNAL OF MOLECULAR LIQUIDS

AUTHORS: Li, YJ; Liu, XY; Wang, BZ; Wang, CY

 

The structural evolution of Li2BeF4 from crystalline to molten states has been investigated by Raman spectroscopic technique with the assist of density functional theory (DFT). The experimental results of temperature-dependent Raman spectra of Li2BeF4 showed that no solid-state phase transformation was taken place during heating process from 298 to 723 K. In the molten state, the structure of BeF42- anion was affected by Li+ cation and environment. For the binary LiF-BeF2 melts with varying LiF/BeF2 ratio, the stretching bands of beryllium-fluorine bonds in molten Raman spectra were deconvolved identified by Gaussian function. When the concentration of BeF2 exceeding 33 mol%, the dimer Be2F73- was formed and dominated the spectrum. It was characterized to have a linear Be-F-Be geometry with two BeF4 moieties bridged by a single fluorine atom. A second anion Be3F104- processing a triple chain structure formed when the content of BeF2 inaeasing to 50 mol%. When the concentration of BeF2 went beyond 60 mol%, the Raman intensity and band width gradually decreased. While the intensity and band width of Raman spectra gradually decreased with the concentration of BeF2 exceeding to 60 mol%, which suggests that the band should be assigned to a hexatomic Be6F186- ring which was similar to the situation in the pure BeF2 network structure. (C) 2020 Elsevier B.V. All rights reserved.

 

LINKS: http://dx.doi.org/10.1016/j.molliq.2020.115208