Local exchange and correlation potentials for electron scattering at solid surfaces

Abstract

Atomic local exchange and correlation potentials for use in LEED, photoelectron diffraction and near edge EXAFS calculations are investigated by comparing the calculated total and differential electron scattering cross sections for Ar, Kr and Xe atoms with experimental data. Four potentials are considered, namely the Xα potential with α = 0.7 (a value appropriate to ground state properties), the Xα potential with a reduced α value of 0.4; the Hara potential and the potential of Lee and Beni. At energies of 100 eV and above, all four potentials give an adequate description of the data. At lower energies ranging from 10 to 60 eV, the Hara potential and the Xα ( α = 0.4) potential remain adequate but the Xα ( α = 0.7) potential and the Lee and Beni potential give very poor correspondence with the data. Since the Lee and Beni potential is theoretically an improvement over the Hara potential within the Local Density Approximation (LDA) we conclude that the LDA itself is inadequate for the description of the scattering of low energy electron from atoms and that the success of the Hara potential must be due to a fortunate cancellation of errors.