Madelung Potential in Surface Reconstruction

Abstract

A reconstructed surface layer on a metal may resemble a two-dimensional ionic crystal. We test this ionic model by estimating the Madelung potential at the sites of foreign anions in mixed layers on nickel. For oxygen on Ni(100), the Madelung potential shifts the electronic energy levels of the ions, and these shifts are consistent with recent experimental data obtained by ion neutralization spectroscopy and photoemission. For sulfur and selenium on Ni(100), reconstruction to form mixed layers is consistent with the data only if the S and Se ions are considerably distorted.