ANALYSIS OF THE CIPSI DCCI APPROACH TO CHARACTERIZE THE HF AND F2 SINGLE BOND

The aim of the present work is to account for the main differential correlation contributions occurring during the bond breaking process of HF and F2 molecules in an accurate and inexpensive way. Starting from the dissociation-consistent configuration interaction (DCCI) scheme by Goddard and co-workers the corresponding contributions are evaluated within the framework reported by Malrieu and co-workers, namely configuration interaction by perturbation with multiconfigurational zeroth-order wavefunction selected by iterative process (CIPSI). In addition, the DCCI scheme has been improved by introducing the dispersion effects associated with the valence MOs adjacent to the bond. The present results show a good agreement with the full Cl data available. Including f functions in the one-electron basis sets, the calculated re (De) values, 1.757 a0 (5.98 eV) and 2.668 a0 (1.64 eV) for HF and F2, reflect a clear trend towards the corresponding experimental data. © 1990.