Linearized Coupled Cluster Correction on the Antisymmetric Product of 1-Reference Orbital Geminals.

We present a linearized coupled cluster (LCC) correction based on a reference state of the antisymmetric product of 1-reference orbital geminals (AP1roG). In our LCC ansatz, the cluster operator is restricted to double or to single and double excitations, as in standard single-reference CC theory. The performance of the AP1roG-LCC models is tested for the dissociation of diatomic molecules in their lowest-lying singlet state (C2, F2, and BN), the symmetric dissociation of the H50 hydrogen chain, and spectroscopic constants of the uranyl cation (UO2 2+). Our study indicates that an LCC correction based on an AP1roG reference function is more robust and reliable than corrections based on perturbation theory, yielding spectroscopic constants that are in very good agreement with theoretical reference data.