Symmetry-adapted perturbation theory applied to interaction-induced properties of collisional complexes

A symmetry-adapted perturbation theory (SAPT) is formulated for interaction-induced electrical properties of weakly bound complexes. Asymptotic (large R) expressions are reported for the contributions to the collision-induced dipole moments and polarizabilities up to and including second order in the intermolecular potential. These long-range expressions require knowledge only of the multipole moments and (hyper)polarizabilities of the isolated monomers. Numerical results are given for the dipole moment of He-H-2 and the polarizability of He-2 and the accuracy of the SAPT approach is examined by comparison with full configuration interaction results. The role of various physical contributions to the dipole moment of He-H-2 and the polarizability of He-2 is investigated. The validity of the long-range approximation and the importance of charge penetration (damping) effects are discussed.