Orientational correlations in liquid carbon tetrabromide: A neutron diffraction and RMC study

Neutron diffraction measurements have been made for liquid carbon tetrabromide (CBr4) and converted to a composite pair correlation function. The results have been analysed using a Reverse Monte Carlo (RMC) technique to study the inter-relation of neighbouring molecules and the influence of molecular shape on the centres correlation function. It is found that the four closest neighbouring molecules have a preferred tetrahedral distribution and the orientation is not strongly ordered relative to the reference molecule although certain geometrical configurations 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 shape contours of the molecule are seen to have a significant influence on the position and orientation of adjacent molecules in an inner sub-shell but the longer range structure is dominated by overall packing effects in the liquid.