RESTRICTED OPEN-SHELL HARTREE-FOCK THEORY

A new formula is introduced for the energy expectation value of multi- determinantal single configuration states with arbitrary open shells i n terms of the 4-indexed electronic repulsion integrals. Applying the variational principle to this expression and introducing 2-indexed Cou lomb and exchange operators, new forms of Hartree-Fock and Hartree-Foc k-Roothaan equations for open shell systems are obtained. They are bas ed entirely on the restricted Hartree-Fack formalism. (C) 1998 Elsevie r Science B.V.