Local spin-density approximation for spin eigenspaces and its application to the excited states of atoms - art. no. 022502

The main objective of this paper is to investigate the applicability of the subspace density-functional theory (SDFT) for the calculation of excited-s tate energies. The exchange and correlation energy density functionals, E-x c(rho), used in the present calculation are local and depend on the polariz ability parameter zeta=2S/N. The deviations of the calculated excited-state energies from their corresponding experimental values range from 0.1% to 0 .8% for systems with more than two electrons, while for the helium isoelect ronic series the corresponding range is from 0.1% to 1.9%. Thus the SDFT ac curacy compares well in most cases with th:dt of the ground-state local-den sity approximation calculations. Virial theorem and other relations concern ing atoms are verified in the context of SDFT calculations. In this paper w e also present a new formulation of the SDFT. Our new formulation alleviate s the initial Kohn and Sham (KS) theory from the constraint of densities re presentable by single Slater determinants. This is an essential development as there are eigenstates of spin and other quantum operators, not represen table by single Slater determinants.