An exact second-order expression for the density functional theory correlation potential for molecules

In this communication we present the exact, local, one-electron, second-order correlation potential for molecules, for use in density functional studies. The correlation potential is represented in a basis set, and when combined with the exact exchange potential, it provides an exchange-correlation potential that is derived exclusively from exact, orbital-dependent expressions. In this sense, such potentials provide an ab initio density functional theory (DFT) that permits convergence to the exact answer as higher order terms are introduced, just as is the case for ab initio correlated methods. Furthermore, this potential includes some dispersion effects that are missing from other DFT potentials. (C) 2001 American Institute of Physics.