Comments on the metal surface from a simple analytic model

Very accurate surface energies and work functions for a semi-infinite jellium can be calculated from a simple and transparent analytic model. The model is a modified version of one proposed by Smith and refined by Ma and Sahni which employs the gradient expansion for the kinetic energy and a one-parameter trial density profile; the modifications are use of a more-realistic profile and a less-profile-sensitive expression for the work function. This model is used to explore the qualitative effects of exchange and correlation on the metal surface properties, as well as the significant quantitative effects of different choices for the bulk correlation energies ε_c(n) which serve as input to the local-density approximation.