An energy functional for surfaces

We propose a simple way of correcting general gradient and local density ap proximation surface energies for errors of these approximations intrinsic t o surfaces by the appropriate use of reference systems with an exponential surface potential v(eff)(z)proportional toe((z/a)). A test of this approach applied to general gradient and local density approximation surface exchan ge energies for half jellium systems removes most of the surface-intrinsic errors and yields excellent results. We suggest that the same procedure wou ld also be successful for surface correlation effects. We conclude with som e general remarks about future directions of density functional theory. (C) 2001 American Institute of Physics.