A NEVER FORM FOR THE EXCHANGE-CORRELATION ENERGY FUNCTIONAL

A new approximate form for the exchange-correlation energy functional is developed. The form is lased on the density matrix expansion (DME) for the exchange functional [R. M. Koehl, G. K. Odom, and G. E. Scuser ia,Mol. Phys. 87, 835 (1996)]. The nonlocal portion of the correlation energy is assumed to have the same general form as that derived for e xchange, while the local portion is taken to be that of the uniform el ectron gas. The resulting formula does not resort to the use of exact- exchange mixing. A Kohn-Sham implementation of this functional is cons tructed and the parameters within the functional are adjusted to minim ize the difference between the theoretical and the experimental data f or a large set of atomic and molecular systems. The results are found to compare favorably with existing functionals, even those which inclu de exact-exchange mixing. (C) 1998 American Institute of Physics.