The adsorption sites of rare gases on metallic surfaces: a review

Abstract

During the past six years, the adsorption geometries of several rare gases in structureshaving several different symmetries on a variety of substrates were determined usinglow-energy electron diffraction (LEED). In most of these studies, a preference is found forthe rare gas atoms to adsorb in the low-coordination sites. Only in the case of adsorptionon graphite has a clear preference for a high-coordination site for a rare gas atom beenfound. This unexpected behaviour is not yet completely understood, although recentdensity functional theory (DFT) calculations for these and similar surfaces suggest thatthis is a general phenomenon. This paper reviews the early studies that were presages ofthe discovery of top site adsorption for rare gases, the discovery itself, and the present stateof understanding of this curiosity. It also details some of the features of the LEEDexperiments and analysis that are specific to the case of rare gas adsorption.