DYNAMIC CORRELATION FOR BIORTHOGONAL VALENCE-BOND REFERENCE STATES

The use of biorthogonal valence bond reference functions in evaluating the correlation energy is investigated. Since the method is not varia tionally bound some care must be taken in defining the reference state to ensure that the variational bound is not violated, some discussion is given to this matter. The procedure adopted here is a matrix eleme nt driven configuration interaction scheme. To reduce the computationa l labour involved, a configuration selection criterion is introduced. The method is tested through its application to the symmetric stretchi ng of HF, H2O2 (B-2(1)) NH, and the singlet-triplet gap in CH2. Compar ison is made with other methods, including full CI. The results show t hat the current method is quite promising.