RELATIVISTIC REGULAR 2-COMPONENT HAMILTONIANS

In this paper, potential-dependent transformations are used to transfo rm the four-component Dirac Hamiltonian to effective two-component reg ular Hamiltonians. To zeroth order, the expansions give second order d ifferential equations (just like the Schrodinger equation), which alre ady contain the most important relativistic effects, including spin-or bit coupling. One of the zero order Hamiltonians is identical to the o ne obtained earlier by Chang, Pelissier, and Durand [Phys. Scr. 34, 39 4 (1986)]. Self-consistent all-electron and frozen-core calculations a re performed as well as first order perturbation calculations for the case of the uranium atom using these Hamiltonians. They give very accu rate results, especially for the one-electron energies and densities o f the valence orbitals.