Convergence acceleration for the Kohn variational method in the presence of a long-range interaction

This paper presents a distorted-wave generalization of the S-matrix version of the Kohn variational principle developed by Zhang, Chu, and Miller [J. Chem. Phys. 88, 10 (1988)]. For scattering in the presence of a long-range interaction, the large-r asymptotic solution to the Schrödinger equation is built into the Kohn variational principle order by order in an effort to accelerate the convergence of the short-range square integrable part of the basis-set expansion. The improvement in the rate of convergence is demonstrated by applying the method to a long-range model potential. Multichannel scattering is discussed.