Further analysis of surface bond lengths measured for chemisorption on metal surfaces

This paper compares bond lengths deduced from the methods of surface crystallography with predictions from the Pauling–Schomaker–Stevenson approach and from a new alternative approach suggested by recent work of Brown and Altermatt. Examples considered are specifically for X—M surface bond lengths where atoms X from groups 16 or 17 are adsorbed on well-defined surfaces of a metal M. The alternative approach introduced here is parametrised with reference to structural data from solid compounds of formula MX. The two predictive approaches considered, when used together, appear to be quite adequate for guiding choices of trial model structures to be included in surface crystallographic analyses with low-energy electron diffraction (LEED); also they seem reasonable for checking the general reliability (or otherwise) of surface bond length data. Two further features introduced by this work are (i) evidence that the Cl—Ag distance reported by LEED for Cl adsorbed on the Ag(100) surface is broadly consistent with the structure of solid AgCl; (ii) evidence for S adsorbed on the Fe(110) surface that these analyses can guide investigations of lateral relaxations of surface metal atoms. As more reliable structural data become available, extensions of these analyses should help to identify the finer details in X—M bond lengths which result from the special coordination arrangements occurring at surfaces.