Kohn-Sham theory for ground-state ensembles - art. no. 093001

An electron density distribution n(r) which can be represented by that of a single-determinant ground state of noninteracting electrons in an external potential v(r) is called pure-state v-representablc (P-VR). Most physical electronic systems are P-VR. Systems which require a weighted sum of severa l such determinants to represent their density are called ensemble v-repres entable (E-VR). This paper develops formal Kohn-Sham equations for E-VR phy sical systems, using the appropriate coupling constant integration. It also derives local density- and generalized gradient approximations, and condit ions and corrections specific to ensembles.