VALENCE DENSITY FUNCTIONALS

We derive an extension of the Hohenberg-Kohn (HK) theorem which applies to the valence electrons only, excluding core states. The energy functional of the valence electron density is minimized giving a variational bound on the total ground-state energy. A Kohn-Sham-type approximation suggests treating valence states by the local density approximation (LDA) and the core states by Hartree-Fock. The functional can be used to generate pseudopotentials or to perform all-electron calculations beyond conventional LDA. Our formalism also yields a simple derivation of the HK theorem for Dirac electrons.