Dynamical correlation within the Interacting Quantum Atoms method through coupled cluster theory

The Interacting Quantum Atoms (IQA) approach is an energy partition of an electronic system which has provided new understandings and insightful information about diverse chemical systems and processes from Hartree–Fock, CASSCF as well as truncated and full CI wavefunctions. Nonetheless, the unavailability of an implementation of IQA relying on size extensive correlated methods such as coupled cluster or Møller–Plesset perturbation theory, has prevented the application of this procedure to the study of molecular systems in which these models of electronic structure are necessary to obtain accurate results. This paper uses first and second-order density matrices consistent with a closed shell coupled cluster energy to carry out the IQA splitting. The presented developments are tested and discussed using H2, N2, H2O and CO as representative examples. It is our hope that the implementations discussed in this paper would give new insights in the study of chemical bonding, intermolecular interactions and other important phenomena in chemistry for which the consideration of electron correlation is critical.