Full CI Extrapolation: Application to H2O with a Double Zeta Basis Set

Abstract

A previously reported full CI (configuration interaction) extrapolation procedure based on multireference single and double CI, which gave excellent results for H20 at the equilibrium geometry, is extended to two other geometries for which explicit full CI results are known. The technique is shown to provide good results for cases where the SCF (self-consistent field) configuration is not strongly dominant, although degradation of performance is noticeable in these cases. The technique is also used to predict a full CI result for the 21 Al state of H20 with the double zeta basis.