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-ord er correlation potential for molecules, for use in density functional studi es. The correlation potential is represented in a basis set, and when combi ned with the exact exchange potential, it provides an exchange-correlation potential that is derived exclusively from exact, orbital-dependent express ions. In this sense, such potentials provide an ab initio density functiona l 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 mis sing from other DFT potentials. (C) 2001 American Institute of Physics.