Improved quantum theory of many-electron systems. II. The basic method

Abstract

A general method of obtaining accurate and useful many-electron wave functions for atoms and molecules is developed. The method involves the proper optimization of a many-electron function which is an eigen-function of total spin and which satisfies Pauli's principle. The procedure is somewhat similar to that in which one obtains the Hartree-Fock wave function by properly optimizing a Slater determinant. There are three key features of the new method: (1) The wave function remains accurate as the nuclei configuration is changed from the equilibrium configuration to that of the dissociated molecule; (2) the many-electron wave function can be interpreted in an independent-particle scheme; (3) the independent-particle states are no longer always required to be symmetry functions for the spatial symmetry group as in the Hartree-Fock method. In addition, the energy calculated using the new method is always lower than the Hartree-Fock energy, and the method is applicable to states of any total spin and number of particles. Calculations using this method are reported for the H2 and LiH molecules.

Group Members

William A. Goddard III

Charles and Mary Ferkel Professor