Coalescence Conditions as Constraints in Open-Shell SCF Theory

The general coalescence conditions of Pack and Byers Brown are applied to the special case of electron—nucleus coalescence for SCF orbitals in atoms and molecules. Integral coalescence conditions are derived and then used to construct constraints for the variation of the orbitals. The constrained variation leads to new pseudo-eigenvalue equations, which may be solved by combining the methods of parametrization and perturbation.