New cumulative indices which describe the configurational structure and the degree of 'multi-configurationality' of the coupled cluster (CC) wave function have been proposed and tested on some model systems. The indices calculated for the coupled cluster wave functions generated with the CCSD (single and double excitations) and CCSDT (single, double, and triple excitations) models were compared with the corresponding values obtained with the full configuration interaction (FCI) method. The test calculations have concerned cases where the multi-reference character of the wave function increases due to bond stretching.
- Coupled cluster wave function
- Multi-configurational nature
- New indices
ASJC Scopus subject areas
- Molecular Biology
- Condensed Matter Physics
- Physical and Theoretical Chemistry