, and a density dependent interaction potential which gradually changes from a pure metal interaction to a nonmetal interaction, on going from metal state to nonmetal state in the transition region, is used. Well-depth and the position of potential minimum are presented as temperature dependent quantities; their calculated values for the metal state are typically within 5.0% and 0.33% of the experimental value, respectively. The calculated well-depth for nonmetal state is smaller than the experimental value indicating the effect of high pressure T Pρ data used, which pushes a pair of mercury atom further together into the repulsive side.In the transition region, calculated well-depths are 2-3 order of magnitudes larger than for the metal state, and contain a sharp rising edge and a steep falling having a singularity characteristic of phase transition.