Coupling Natural Orbital Functional Theory and Many-Body Perturbation Theory by using non-dynamically correlated canonical orbitals

Mauricio Rodriguez (1) , Ion Mitxelena (2) , Fabien Bruneval (1) , Mario Piris (2)

1 SRMP - Service de recherches de métallurgie physique
2 Donostia International Physics Center - DIPC (SPAIN)

We develop a new family of electronic structuremethods for capturing at the same time thedynamic and non-dynamic correlation effects.We combine natural orbital functional theory(NOFT) and many-body perturbation theory(MBPT) through a canonicalization procedureapplied to the natural orbitals to gain access toany MBPT approximation. We study three dif-ferent scenarios: Corrections based on second-order Møller-Plesset (MP2), Random-PhaseApproximation (RPA), and coupled-cluster sin-gles doubles (CCSD). Several chemical prob-lems involving different types of electron cor-relation in singlet and multiplet spin stateshave been considered. Our numerical tests re-veal that RPA-based and CCSD-based correc-tions provide similar relative errors in molecu-lar dissociation energies (De) to the results ob-tained using a MP2 correction. With respectto the MP2 case, the CCSD-based correctionimproves the prediction, while the RPA-basedcorrection reduces the computational cost.

Domains: Theoretical and/or physical chemistry

Mauricio Rodriguez, Ion Mitxelena, Fabien Bruneval, Mario Piris. Coupling Natural Orbital Functional Theory and Many-Body Perturbation Theory by using non-dynamically correlated canonical orbitals. Journal of Chemical Theory and Computation, 2021, 17 (12), pp.7562. ⟨10.1021/acs.jctc.1c00858⟩. ⟨cea-03516535⟩