Liquid GeBr4. II: Molecular packing and liquid structure

Anomalous scattering data from 1-GeBr4 are compared with theoretical predictions and with several models. Published hard-sphere RISM calculations of the pair correlation functions accurately predict the features of the experimental distribution functions, but discrepancies between theory and experiment are larger than the experimental uncertainty. New calculations with more realistic potentials are needed. The total structure factor of 1-GeBr4 contains a prepeak which is due largely, but not exclusively, to correlations between molecular centers (i.e., germanium atoms). Modeling results indicate that there is strong interlocking of molecules in the liquid and that the Br–Br structure factor is largely determined by the packing of the halogen atoms with the germanium atoms effectively fitting in tetrahedral interstices. Models based on the monoclinic crystal of SnBr4 agree better with the liquid data than models based on the cubic crystal of c-GeBr4, suggesting that GeBr4 undergoes a change in short-range molecular packing on melting.