Double Ionization Potential Equation-of-Motion Coupled-Cluster Approach with Full Inclusion of 4-Hole-2-Particle Excitations and Three-Body Clusters

Abstract

The double ionization potential (DIP) equation-of-motion (EOM) coupled-cluster (CC) method with a full treatment of 4-hole-2-particle (4$h$-2$p$) correlations and triply excited clusters, abbreviated as DIP-EOMCCSDT(4$h$-2$p$), and its approximate form called DIP-EOMCCSD(T)(a)(4$h$-2$p$) have been formulated and implemented in the open-source CCpy package available on GitHub. The resulting codes work with both nonrelativistic and spin-free scalar-relativistic Hamiltonians. By examining the DIPs of a few small molecules, for which accurate reference data are available, we demonstrate that the DIP-EOMCCSDT(4$h$-2$p$) and DIP-EOMCCSD(T)(a)(4$h$-2$p$) approaches improve the results obtained using the DIP-EOMCC methods truncated at 3$h$-1$p$ or 4$h$-2$p$ excitations on top of the CC calculations with singles and doubles.

8 pages and 4 tables. Supplementary Material as an ancillary file. This article has been accepted for publication in the Journal of Chemical Physics. After it is published, it will be found at

References in corpus (5)

• Recent developments in the PySCF program package
• Quantum Package 2.0: An Open-Source Determinant-Driven Suite of Programs
• Hybrid stochastic-deterministic calculation of the second-order perturbative contribution of multireference perturbation theory
• Reference Energies for Valence Ionizations and Satellite Transitions
• Anomalous propagators and the particle-particle channel: Hedin's equations

Cited by in corpus (3)

• Anomalous propagators and the particle-particle channel: Bethe-Salpeter equation
• Structure and dynamics of open-shell nuclei from spherical coupled-cluster theory
• Double Electron Attachment and Double Ionization Potential Equation-of-Motion Coupled-Cluster Approaches with Full and Active-Space Treatments of 4-Particle-2-Hole and 4-Hole-2-Particle Excitations and Three-Body Clusters