Equation-of-motion coupled-cluster method with double electron-attaching operators: Theory, implementation, and benchmarks

Sahil Gulania; Eirik F Kjønstad; John F Stanton; Henrik Koch; Anna I Krylov

doi:10.1063/5.0041822

Equation-of-motion coupled-cluster method with double electron-attaching operators: Theory, implementation, and benchmarks

J Chem Phys. 2021 Mar 21;154(11):114115. doi: 10.1063/5.0041822.

Authors

Sahil Gulania¹, Eirik F Kjønstad², John F Stanton³, Henrik Koch⁴, Anna I Krylov¹

Affiliations

¹ Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA.
² Department of Chemistry, Norwegian University of Science and Technology, 7491 Trondheim, Norway.
³ Quantum Theory Project, Departments of Chemistry and Physics, University of Florida, Gainesville, Florida 32611, USA.
⁴ Scuola Normale Superiore, Piazza dei Cavaleri 7, 56126 Pisa, Italy.

PMID: 33752380
DOI: 10.1063/5.0041822

Abstract

We report a production-level implementation of the equation-of-motion (EOM) coupled-cluster (CC) method with double electron-attaching (DEA) EOM operators of 2p and 3p1h types, EOM-DEA-CCSD. This ansatz, suitable for treating electronic structure patterns that can be described as two-electrons-in-many orbitals, represents a useful addition to the EOM-CC family of methods. We analyze the performance of EOM-DEA-CCSD for energy differences and molecular properties. By considering reduced quantities, such as state and transition one-particle density matrices, we compare EOM-DEA-CCSD wave functions with wave functions computed by other EOM-CCSD methods. The benchmarks illustrate that EOM-DEA-CCSD is capable of treating diradicals, bond-breaking, and some types of conical intersections.