Local Energy Decomposition of Open-Shell Molecular Systems in the Domain-Based Local Pair Natural Orbital Coupled Cluster Framework

Ahmet Altun; Masaaki Saitow; Frank Neese; Giovanni Bistoni

doi:10.1021/acs.jctc.8b01145

Local Energy Decomposition of Open-Shell Molecular Systems in the Domain-Based Local Pair Natural Orbital Coupled Cluster Framework

J Chem Theory Comput. 2019 Mar 12;15(3):1616-1632. doi: 10.1021/acs.jctc.8b01145. Epub 2019 Feb 18.

Authors

Ahmet Altun¹, Masaaki Saitow², Frank Neese¹, Giovanni Bistoni¹

Affiliations

¹ Max-Planck-Institut für Kohlenforschung , Kaiser-Wilhelm-Platz 1 , D-45470 Mülheim an der Ruhr , Germany.
² Department of Chemistry, Graduate School of Science , Nagoya University , 1-5 Chikusa-ku , 464-8602 Nagoya , Japan.

Abstract

Local energy decomposition (LED) analysis decomposes the interaction energy between two fragments calculated at the domain-based local pair natural orbital CCSD(T) (DLPNO-CCSD(T)) level of theory into a series of chemically meaningful contributions and has found widespread applications in the study of noncovalent interactions. Herein, an extension of this scheme that allows for the analysis of interaction energies of open-shell molecular systems calculated at the UHF-DLPNO-CCSD(T) level is presented. The new scheme is illustrated through applications to the CH₂···X (X = He, Ne, Ar, Kr, and water) and heme···CO interactions in the low-lying singlet and triplet spin states. The results are used to discuss the mechanism that governs the change in the singlet-triplet energy gap of methylene and heme upon adduct formation.