<i>C</i>_2<i>V</i> Insertion pathway for BeH₂: A test problem for the coupled‐cluster single and double excitation model

Abstract

Abstract The coupled‐cluster single and double excitation model ( CCSD ) is applied to an energy path for the insertion of Be into H 2 and compared to the full configuration interaction ( FCI ) and full valence–multiconfiguration self‐consistent field ( FV – MCSCF ) results. This model problem is a severe test of a single‐reference‐function correlated method since two configurations are heavily weighted in the FCI description. CCSD is demonstrated to describe the FCI results using a single reference function which, however, changes orbital characteristics along the sampling path. In this case CCSD gives excellent agreement with the FCI results.