Many‐body theory of exchange effects in intermolecular interactions. Second‐quantization approach and comparison with full configuration interaction results

摘要: Explicitly connected many‐body perturbation expansion for the energy of first‐order exchange interaction between closed‐shell atoms or molecules is derived. The influence intramonomer electron correlation accounted by a in terms Mo/ller–Plesset fluctuation potentials WA and WB monomers nonperturbative coupled‐cluster type procedure. Detailed orbital expressions corrections first second order WA+WB are given. Our method leads to novel energies which hybrid integrals do not appear. These expressions, involving only Coulomb overlap integrals, structurally similar standard theory polarization energies. Thus, can be easily coded suitably modifying existing induction dispersion codes. As test our we have performed calculations first‐...