Excitation energies through the locally renormalized equation-of-motion formalism: singles and doubles model.
The stationary conditions obtained from approximate coupled-cluster functional derived from the numerator-denominator connected expansion (NDC) [K. Kowalski and P. Piecuch, J. Chem. Phys. 122, 074107 (2005)] are employed to calculate the linear response of cluster amplitudes. A simple scheme that involves singly and doubly excited amplitudes, termed locally renormalized equation-of-motion approach with singles and doubles (LR-EOMCCSD), is compared with other excited-state methods that include up to two-body operators in the wave function expansion. In particular, the impact of the local denominators on the excitation energies is discussed in detail. Several benchmark calculations on the CH(+), C(2), N(2), O(3), and ClOCl molecules are presented to illustrate the performance of the LR-EOMCCSD approach.
Kowalski
Karol
K
William R. Wiley Environmental Molecular Sciences Laboratory, Battelle, Pacific Northwest National Laboratory, K8-91, P.O. Box 999, Richland, WA 99352, USA. karol.kowalski@pnl.gov