Structural variation of expanded fluid mercury during M-NM transition: A Reverse Monte Carlo study

The structure of fluid Hg during the metal-non-metal transition has been modelled by Reverse Monte Carlo simulation in terms of the structural factors S(Q) measured by X-ray diffraction at SPring-8. The full region of S(Q) including S(0) was employed in the simulation so as to take the effect of fluctuation phenomenon into account. The modelling reveals that as the M-NM transition is approached, the distribution of coordination numbers, P(N), of the first-neighbor shell broadens obviously and shifts to lower values, supporting the speculation of Franz's model. Furthermore, the coordination number PS(N), denoted for atoms with a shorter bond, changes markedly in width and average value, while much smaller is found for that of longer bond as the density decreases. The variation of PS(N) of the atoms with the shorter bond are directly related to the M-NM transition of fluid Hg.