Structure and binding of ionic clusters in Th and Zr chloride melts

Abstract

We discuss microscopic ionic models for the structure and the binding of small clusters which may exist as structural units in molten ThCl4 and ZrCl4 and in their mixtures with alkali halides according to Raman scattering studies of Photiadis and Papatheodorou. The models are adjusted to the two isolated tetrahedral molecules. Appreciably higher ionicity is found for ThCl4 than for ZrCl4, and this fact underlies the strikingly different behaviour of the two systems in the dense liquid state - in particular, a molecular-type structure for molten ZrCl4 against a structure including charged oligomers in molten ThCl4.