The performances of three common gradient-level exchange–correlation functionals for metallic bulk, surface and vacancy systems were compared. It was found that approximations which, by construction, gave similar results for the jellium surface, exhibited large deviations for realistic systems. The particular charge density and density gradient dependence of the exchange–correlation energy densities were shown to be the reason behind the differences obtained. These findings confirmed that both the global (total energy) and the local (energy density) behaviour of the exchange–correlation functional should be monitored for a consistent functional design.

Density Functional Study of Vacancies and Surfaces in Metals. L.Delczeg, E.K.Delczeg-Czirjak, B.Johansson, L.Vitos: Journal of Physics - Condensed Matter, 2011, 23[4], 045006