Broken Symmetry in the Local-Spin-Density Approximation and Its Application to Relativistic Atoms

The ground state of the ($d^4{s}^2$) configuration shifts by 1.725 eV relative to that of the ($d^{5}s$) on going from Mo to W. This shift, which arises mainly from relativistic contributions to the W energy, is calculated with 2% accuracy by use of the authors' relativistic pseudopotential and the local-spin-density approximation. That the single determinantal broken-symmetry local-spin-density approximation wave function accounts for the spin-orbit energy, which otherwise could be obtained from the spin-orbit mixing of several multideterminantal terms, may be surprising.