ORIENTATIONAL CORRELATIONS IN LIQUID CARBON TETRABROMIDE - A NEUTRON-DIFFRACTION AND RMC STUDY

Neutron diffraction measurements have been made for liquid carbon tetr abromide (CBr4) and converted to a composite pair correlation function . The results have been analysed using a Reverse Monte Carlo (RMC) tec hnique to study the inter-relation of neighbouring molecules and the i nfluence of molecular shape on the centres correlation function. It is found that the four closest neighbouring molecules have a preferred t etrahedral distribution and the orientation is not strongly ordered re lative to the reference molecule although certain geometrical configur ations can be identified. Other molecules in close proximity are less ordered and create a loosely-packed hexagonal structure for the broad distribution within the first co-ordination shell. In effect, the shap e contours of the molecule are seen to have a significant influence on the position and orientation of adjacent molecules in an inner sub-sh ell but the longer range structure is dominated by overall packing eff ects in the liquid.