Extensions of the LSD approximation in density functional calculations

Multiplet splittings of first row and iron series atoms and ions have been calculated using two modifications of the local spin density (LSD) functional approach. (a) The energies of individual states are related to linear combinations of energies calculated from single determinants. (b) The spin dependent part of the functional is constructed to reflect the symmetry between electrons and holes. Agreement with experiment is improved significantly and trends are described remarkably well. There is a general tendency for the LSD approximation to overestimate the relative stability of states with greater p- and d-character and singlet–triplet splittings for sd-configurations.