Perturbation theory calculations of intermolecular interaction energies

Abstract

Intermolecular interactions play an essential role in determining the structure and conformation of biomolecules, in particular, in aqueous solutions. With the recent development of computer capabilities, it is now possible to calculate the interactions of biologically relevant molecules using the standard self-consistent field approximation. For most systems, this approximation is not sufficient and the correlation component of the interaction energy must be included. Unfortunately, the supermolecular method, which is mostly used to calculate the intermolecular interactions at the correlated level, is plagued by the basis-set superposition error and does not provide any physical interpretation of the interaction energy. An alterative approach is to use the symmetry-adapted (exchange) perturbation theory developed by us. This theory is free from the basis-set superposition error, provides a clear physical picture of the interaction energy, and involves less computational effort than does a standard many-body perturbation theory calculation of equivalent order. We have developed a system of ab initio computer codes performing calculations for arbitrary molecules. For small systems—where the accuracy could be tested—our results are in excellent agreement with experiment. Large-scale calculations performed for systems such as (H2O)2, (HF)2, and uracil…water demonstrate the high efficiency and accuracy of our method.