Second-order truncated functional expansions of energy density functionals- art. no. 054501

Parr and Liu [Chem. Phys. Lett.. 276. 164 (1997)], showed that the electron -electron repulsion functional V-ce[rho] can be expressed in terms of its f irst and second functional derivatives under certain assumptions. Starting from this expansion it is shown that with the same assumptions, the density -functional exchange ;energy E-x[rho], correlation energy E-c[rho], and the kinetic contribution to the correlation energy T-c[rho], can each be expre ssed in terms of their first and second functional derivatives only. It is pointed out that some expansions of density functionals proposed in the lit erature are not compatible with the expressions derived.