A new procedure for Roothaan's symmetry-restricted open-shell SCF method

Abstract

Roothaan's symmetry-restricted open-shell SCF method is derived without the use of lagrangian multipliers for a general case of one open shell per symmetry. A single Fock operator is formulated converging to the same eigenfunctions and eigenvalues as obtained by the standard double- eigenvalue method of Roothaan. Comparisons are made with other formulations of the method, and test calculations are provided for singly and doubly ionized states of methane in the neutral ground-state geometry.