A GENERALIZED MULTISTRUCTURAL DESCRIPTION OF THE GROUND-STATE OF OZONE AND WATER-MOLECULES

Generalized multistructural (GMS) wavefunctions are presented for the ground state of ozone and water molecules at the equilibrium geometry. For the ozone molecule the results confirm the diradical character of the ground state and show that the contribution of the zwitterionic s tructures is negligible. The reasons for the discrepancy between the M O and VB descriptions of the molecule are also presented. For the wate r molecule the GMS results also show that once orbital optimization is considered there is no need to include polar structures in a VB-type expansion. Also, a great deal of correlation energy can be recovered u sing very simple and compact GMS wavefunctions.