Ab initio floating occupation molecular orbital-complete active space configuration interaction: An efficient approximation to CASSCF

• Published in: The Journal of chemical physics Vol. 132; no. 23; pp. 234102 - 234102-10
• Main Authors: Slavíček, Petr, Martínez, Todd J.
• Format: Journal Article
• Language: English
• Published: United States American Institute of Physics 21.06.2010
• ISSN: 0021-9606; 1089-7690; 1089-7690
• DOI: 10.1063/1.3436501

We have implemented a complete active space configuration interaction method (CASCI) based on floating occupation molecular orbitals (FOMOs) at the ab initio level. The performance of this FOMO-CASCI method was investigated for potential applications in photochemistry and photodynamics. We found that FOMO-CASCI often represents a good approximation to the state-averaged complete active space self-consistent field (SA-CASSCF) method. FOMO-CASCI is therefore an attractive alternative for use in ab initio photodynamics. The method is more efficient and more stable than SA-CASSCF. We also discuss some problematic cases for the FOMO-CASCI approach. Possible extensions of the FOMO-CASCI approach are discussed briefly.