RMC modelling of the structure of expanded liquid mercury along the co-existence curve

The structure factors of liquid Hg at 13 temperatures/pressures along the liquid-vapour co-existence curve have been modelled using the reverse Monte Carlo (RMC) method. The resulting configurations are consistent with the idea that the liquid contains atoms which can be considered as being in a 'metallic' environment, characterized by a larger number of near neighbours at a relatively short distance, and atoms which are in a 'semiconducting' environment, characterized by a smaller number of neighbours at a slightly longer distance. As the temperature increases and the density decreases, the proportion of 'metallic' atoms decreases. The metal-non-metal transition at rho(M-NM) approximate to 9 g cm(-3) (0.027 Angstrom(-3)) may be considered as a percolation transition in the metallic bond network. At lower densities the metal atoms occur in isolated clusters, and there is some evidence that the critical point at rho(c) = 5.8 g cm(-3) (0.0174 Angstrom(-3)) coincides with the disappearance of these clusters.