Kinetic-energy functionals studied by surface calculations

The self-consistent jellium model of metal surfaces is used to study the accuracy of a number of semilocal kinetic-energy functionals for independent particles. It is shown that the poor accuracy exhibited by the gradient expansion approximation and most of the semiempirical functionals in the low density, high gradient limit may be subtantially improved by including locally a von Weizsäcker term. Based on this, we propose a simple one-parameter Padé’s approximation, which reproduces the exact Kohn-Sham surface kinetic energy over the entire range of metallic densities.