title: Linear-response theory for Mukherjee's multireference coupled-cluster method: static and dynamic polarizabilities.
abstract: The formalism of response theory is applied to derive expressions for static and dynamic polarizabilities within the state-specific multireference coupled-cluster theory suggested by Mukherjee and co-workers (Mk-MRCC) [J. Chem. Phys. 110, 6171 (1998)]. We show that the redundancy problem inherent to Mk-MRCC theory gives rise to spurious poles in the Mk-MRCC response functions, which hampers the reliable calculation of dynamic polarizabilities. Furthermore, we demonstrate that in the case of a symmetry-breaking perturbation a working response theory is obtained only if certain internal excitations are included in the responses of the cluster amplitudes. Exemplary calculations within the singles and doubles approximation (Mk-MRCCSD) are carried out on aryne compounds to illustrate the impact of a multireference ansatz on the polarizability.
authors.affiliation: Institut für Physikalische Chemie, Johannes Gutenberg-Universität Mainz, D-55099 Mainz, Germany. jagau@uni-mainz.de
authors.forename: Thomas-C
authors.initials: TC
authors.lastname: Jagau
authors.forename: Jürgen
authors.initials: J
authors.lastname: Gauss