Abstract
Many-body perturbation theory for a direct calculation of the electrostatic interaction energy is developed. Since no multipole expansion is used, the obtained electrostatic energy includes the short-range contributions resulting from the overlap (penetration) of monomers’ charge distributions. The influence of intramonomer electronic correlation is accounted for by the perturbation expansion in terms of the Mo/ller–Plesset type fluctuation potentials for the interacting molecules. Two types of expansions are introduced: one based on the standard Mo/ller–Plesset expansion of the electron density, and the second accounting for the perturbation induced modifications of the monomer’s Fock operators, i.e., for the so-called response or orbital relaxation effects. Explicit orbital expressions for the terms through the fourth order in the intramonomer fluctuation potentials are derived. In this way the leading three-particle correlation contribution to the electrostatic energy is taken into account. Numerical results of perturbative calculations through the fourth order for the He2, (H2)2, and He–H2 systems are presented and compared with the complete configuration interaction results obtained using the same basis sets. It is found that the convergence of the many-body perturbation expansion of the electrostatic energy is fast. The sum of corrections through the fourth order reproduces to within few percent the correlation part of the electrostatic energy computed with the full configuration interaction wave function.
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call