Theoretical Calculation for the Hugoniot Curves of Liquid Helium

The variational fluid perturbation theory is used to calculate the single and double shock Hugoniot curves of liquid helium by means of a two-body potential function. It is found that the theoretical predictions are 30%～50% higher than the measurements at the same volume. It shows that the effective potential of two atoms, which are at high densities and temperatures, is much lower than that of two isolated ones. The physical mechanism which probably causes this unusual soften phenomena and its theoretical treatment methods are discussed as well.