Hybrid approach to relativistic Gaussian basis functions: Theory and applications

We present a hybrid method to solve the relativistic Hartree-Fock-Roothan e quations where the one- and two-electron radial integrals are evaluated num erically by defining the basis functions on a grid. This procedure reduces the computational costs in the evaluation of two-electron radial integrals. The orbitals generated by this method are employed to compute the ionizati on potentials, excitation energies, and oscillator strengths of alkali-meta l atoms and elements of group IIIA through second-order many-body perturbat ion theory. The computed properties are in excellent agreement with the exp eriment and other correlated theories. [S1050-2947(99)10902-8].