The van der Waals potential of mercury dimer

Both the equilibrium distance Re and the well depth De of the mercury dimer potential from a recent relativistic CCSD(T) calculation fall within the error bounds of experiment. With this set of (Re, De), the entire potential curve can be determined by the dispersion coefficients with the Tang–Toennies (TT) potential model without further fitting. The spectroscopic constants calculated from this potential are in excellent agreement with experiment. In the van der Waals well region, there is no discernible difference between the TT potential and the multi-parameter least-square fitted extented Lennard Jones potential. The TT potential has the advantage of being physically transparent and asymptotically approaching to the correct dispersion series.