Theoretical analysis and comparison of unitary coupled-cluster and algebraic-diagrammatic construction methods for ionization

Hodecker, ManuelKTH,Teoretisk kemi och biologi,Heidelberg Univ, Interdisciplinary Ctr Sci Comp, Neuenheimer Feld 205, D-69120 Heidelberg, Germany. (författare)

QC 20220315
This article describes a novel approach for the calculation of ionization potentials (IPs), or, more generally, electron-detachment energies, based on a unitary coupled-cluster (UCC) parameterization of the ground-state wave function. Explicit working equations for a scheme referred to as IP-UCC3 are given, providing electron-detachment energies and spectroscopic amplitudes of electron-detached states dominated by one-hole excitations correct through third order. In the derivation, an expansion of the UCC transformed Hamiltonian involving Bernoulli numbers as expansion coefficients is employed. Both the secular matrix and the effective transition moments are shown to be essentially equivalent to the strict third-order algebraic-diagrammatic construction scheme for the electron propagator (IP-ADC). Interestingly, due to the Bernoulli expansion, neglecting triple substitutions in the UCC expansion manifold does not affect the third-order consistency of the IP-UCC effective transition moments. Finally, the equivalence between ADC and UCC excited-state schemes is shown to not hold in fourth or higher order due to a different treatment of the correlated excited-state basis.

Dempwolff, Adrian L.Heidelberg Univ, Interdisciplinary Ctr Sci Comp, Neuenheimer Feld 205, D-69120 Heidelberg, Germany. (författare)
Schirmer, JochenHeidelberg Univ, Theoret Chem, Neuenheimer Feld 229, D-69120 Heidelberg, Germany. (författare)
Dreuw, AndreasHeidelberg Univ, Interdisciplinary Ctr Sci Comp, Neuenheimer Feld 205, D-69120 Heidelberg, Germany. (författare)
KTHTeoretisk kemi och biologi (creator_code:org_t)

Av författaren/redakt...: Hodecker, Manuel; Dempwolff, Adria ...; Schirmer, Jochen; Dreuw, Andreas

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