Liquid-vapor coexistence curve and fluid structure

Liquid expands to gas under continuous density change at temperatures higher than the liquid-vapor critical point. In this article, we investigate the structure of supercritical fluids for four types of interatomic potentials by molecular dynamics simulation. First, we draw the liquid-vapor coexistence curve on temperature-density plane. The law of rectilinear diameter is fulfilled for all potentials. The coexistence curves scaled by critical values are identical with one another except for typical liquid state. Next, we calculate pair distribution functions of supercritical fluids and find that the fluids expand inhomogeneously.