Transition moments for STEOM-CCSD with core triples

Abstract

Similarity transformed equation-of-motion coupled cluster theory (STEOM-CC) is an alternative approach to equation-of-motion coupled cluster theory for excited states (EOMEE-CC) which uses a second similarity transformation of the Hamiltonian, followed by diagonalization in a small (CI singles-like) excitation space, even when single and double excitations are included in the transformation. In addition to vertical excitation energies, transition moments measure the strength of the interactions between states determining absorption, emission, and other processes. In STEOM-CCSD, transition moments are calculated in a straight-forward manner as biorthogonal expectation values using both the left- and right-hand solutions, with the main difference from EOMEE-CC being the inclusion of the transformation operator. We recently developed an extension of STEOM-CCSD to core excitations, CVS-STEOM-CCSD+cT, which includes triple excitations and the well-known core-valence separation for the core ionization potential calculations. In this work, we derived transition moments for core-excited states with core triple excitations, including both ground-to-core-excited and valence-to-core-excited transitions. The improvement of the computed transition moments of the CVS-STEOM-CCSD+cT method is compared to standard CVS-STEOMEE-CCSD and CVS-EOMEE-CCSD for our previously published small molecule benchmark set.

References in corpus (6)

• Similarity transformed equation of motion coupled cluster theory revisited: a benchmark study of valence excited states
• An analysis of the performance of coupled cluster methods for core excitations and core ionizations using standard basis sets
• Reliable transition properties from excited-state mean-field calculations
• Transition-Potential Coupled Cluster
• Accurate core-excited states via inclusion of core triple excitations in similarity-transformed EOM theory
• Transition-Potential Coupled Cluster II: Optimization of the Core Orbital Occupation Number

Cited by in corpus (1)

• Elucidating Many-Body Effects in Molecular Core Spectra through Real-Time Approaches: Efficient Classical Approximations and a Quantum Perspective