Molecular MCSCF calculations by direct minimization

Abstract

Calculations on H₂O using the single excitation MCSCF method are described. Results are given for equilibrium geometry calculations using a number of basis sets. The energy lowering on carrying out the MCSCF, equivalent to 22 per cent of the estimated correlation energy, is found to be independent of the basis set. A compact representation of the wavefunction using a singular value decomposition method is described and illustrated.