Projection operator in the multiconfiguration Dirac-Fock method

Convergence problems encountered in Multi-Configuration Dirac-Fock calculations using standard finite-difference techniques to solve differential equations are shown to originate from lack of positive-energy projection operators. A new numerical method is proposed which highlights the effects of the negative energy continuum, and can be used to project it out. It is shown that after projection all numerical problems vanish, and that very good convergence is obtained for high Z (up to 130), even when the Gaunt interaction is made self-consistent. Results for the ground state of two electron ions are presented. (orig.)