Ionic monolayers on metals: II. neutral mixed layers and surface reconstruction

Abstract

Mixed layers of ions on a metal crystal surface are important in adsorption and corrosion. We consider reconstructed periodic layers on Ni, and use a modified Born-Haber cycle to make semi-quantitative estimates of heats of adsorption. For O, S, and Se atoms in neutral mixed layers on the (100) and (111) Ni planes, our estimated heats of adsorption have the right sign and magnitude if ionic charges are large. We make the novel suggestion that negative Ni ions are important in some of the structures. Also, we propose a new distinction between reconstruction and true corrosion, and we conclude that metal-metal bonding is the characteristic feature of reconstructed layers. We summarize our findings with a brief comparison of ionic layers of the two kinds.