Second-quantization-based perturbation theory for intermolecular interactions without basis set superposition error

Abstract

A new formalism is proposed for calculating perturbation energy corrections for the case of two interacting molecules at any distance. Second-quantization formalism ensures that the wavefunctions are automatically properly antisymmetric. The approach is based on the recent “chemical Hamiltonian” method, permitting basis set superposition (counterpoise) errors to be excluded from the beginning. The zeroth-order wavefunctions are right eigenfunctions of the formally non-Hermitean unperturbed Hamiltonian appearing in this formalism, and the perturbational problem is handled by introducing a biorthogonal (reciprocal) basis set.