A simple semiempirical potential for two-body multielectron systems is developed. The repulsion is obtained from the exchange energy that is calculated with the surface integral method. The main component of the attraction comes from the second-order polarization energy given by the damped dispersion series. The small contributions of the first-order polarization energy and the overlap integrals to the van der Waals potential are examined. Without any adjustable parameters, this theory is shown to give accurate potential curves for the He-2, Ne-2, and Ar-2 systems. By absorbing the first-order polarization energy into the exchange energy expression and neglecting the small contribution of the overlap integrals, this theory reduces to the successful Tang-Toennies potential model. (C) 1997 American Institute of Physics.