Issue 10, 2000

Excitation energies and transition moments by the multireference averaged quadratic coupled cluster (MR-AQCC) method

Abstract

The MR-AQCC (multireference averaged quadratic coupled cluster) and the MR-ACPF (multireference averaged coupled pair functional) methods can be considered as size-extensivity corrected MR-CISD procedures. So far, they have been applied mostly to ground state calculations of a given symmetry. By formulating MR-AQCC and MR-ACPF in terms of a diagonal shift to the Hamiltonian this restriction is removed. In order to compute transition moments, linear response theory (LRT) is used since there is no wavefunction defined within these methods. A LRT-compliant variant of MR-AQCC and MR-ACPF is developed which allows a consistent formulation of transition energies and moments. In calculations on CH2, CH+ and C2 (where full CI results are available) it is shown that MR-AQCC brings about a substantial improvement for excitation energies and transition moments as compared to MR-CISD.

Additions and corrections

Article information

Article type
Paper
Submitted
10 Jan 2000
Accepted
16 Mar 2000
First published
02 May 2000

Phys. Chem. Chem. Phys., 2000,2, 2067-2073

Excitation energies and transition moments by the multireference averaged quadratic coupled cluster (MR-AQCC) method

P. G. Szalay, T. Müller and H. Lischka, Phys. Chem. Chem. Phys., 2000, 2, 2067 DOI: 10.1039/B000224K

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