Knowledge Bank

A series of Multi-reference Configuration Interaction (MR-CI) calculations has been undertaken to study the general convergence properties of MR-CI energies to the full CI energy. The Complete Active Space SCF (CASSCF) method has been used for determining the reference spaces and optimizing the molecular orbitals. Results will be reported for three points on a double-zeta, ground state potential surface of $H2O$ and an $80$ orbital calculation on $(H2)2$.Comparisons to the full CI results and to a series of single-reference CI calculations will be presented. It will be shown that for these systems, the MR-CI method provides a balanced treatment of a potential surface.