A Relativistic Four- and Two-component Generalized-active-space Coupled Cluster Method

Abstract

Abstract We present an overview of our recent developments of relativistic generalized-active-space coupled cluster and its initial applications to heavy-element systems. The new genuinely string-based method may treat coupled cluster expansions of general order and simulate multi-reference expansions by including higher excitations in properly constructed active spinor spaces. The four-component Dirac-Coulomb Hamiltonian or any approximation to it may be employed, and the underlying spinors are assumed and required to be time-reversal partners. The capability of the new approach is demonstrated and discussed in sample applications to HBr and BiH.