van der Waals (vdW) interaction has been described with a Lennard-Jones potential for decades in molecular mechanics. Here, we report a new potential function Exp-PE from quantum mechanical derivation for vdW interactions for molecular mechanic simulation. High-order ab initio calculations and experimental atomic force microscopy measurements have been used to test its feasibility, and the results suggest that this formula is simple, accurate, and transferable. This new potential function is capable of upgrading the traditional force fields especially for the applications involving vdW interactions.