Half-projected Hartree-Fock calculations on several small molecules

Abstract

The half-projected Hartree-Fock (HPHF) method is examined with respect to its ability to obtain molecular correlation, describe molecular potential energy surfaces, and provide a one particle basis for more elaborate treatments. The equivalence, aside from questions of efficiency, of two different HPHF algorithms is demonstrated. The results of calculations on H2O, C2, N2, and CH2 indicate that the performance of the HPHF method, with spin projection in appropriate cases, is roughly equivalent to limited MCSCF treatments. In particular, (1) a small but important fraction of the correlation energy, (2) qualitatively correct potential energy surfaces, and (3) good one particle orbital bases are obtained. © 1981 American Institute of Physics.