Density Functional Reformulation of Molecular Orbital Theories

Abstract

This chapter discusses molecular orbital theories: density driven self- consistent field theory; and density driven self- consistent field theory (fomalism) followed by the construction of one- particle wavefunctions. The molecular orbital theories, such as self-consistent field, configuration interaction and multi-configurational, constitute minimization of the energy functional. The formalism presented in the chapter can be easily extended to other molecular orbital theories. One can obtain explicit expressions for the exclusion potential and the associated variational equations for the auxiliary functions and the variational coefficients. This allows approximating the exact pseudo- Schrodinger equation for the density amplitude up to any desired degree of accuracy. Because the density amplitude is a function of only three Cartesian coordinates, the equation can be solved numerically. The auxiliary functions can be approximated by finite basis sets. These bases can be of a significantly lower quality that the bases currently used in an ab initio calculations. Another possibility offered by the present formalism is the analysis of the results of molecular orbital calculations in terms of the Pauli and exchange-correlation potentials.