title: General active space commutator-based coupled cluster theory of general excitation rank for electronically excited states: implementation and application to ScH.
abstract: We present a new implementation of general excitation rank coupled cluster theory for electronically excited states based on the single-reference multi-reference formalism. The method may include active-space selected and/or general higher excitations by means of the general active space concept. It may employ molecular integrals over the four-component Lévy-Leblond Hamiltonian or the relativistic spin-orbit-free four-component Hamiltonian of Dyall. In an initial application to ground- and excited states of the scandium monohydride molecule we report spectroscopic constants using basis sets of up to quadruple-zeta quality and up to full iterative triple excitations in the cluster operators. Effects due to spin-orbit interaction are evaluated using two-component multi-reference configuration interaction for assessing the accuracy of the coupled cluster results.
authors: Laboratoire de Chimie et Physique Quantiques, IRSAMC, Université Paul Sabatier Toulouse III, 118 Route de Narbonne, F-31062 Toulouse, France.
authors: Mickaël
authors: M
authors: Hubert
authors: Jeppe
authors: J
authors: Olsen
authors: Jessica
authors: J
authors: Loras
authors: Timo
authors: T
authors: Fleig