STRUCTURE MAPS OF SURFACE STRUCTURES

Abstract

The adatom positions of adsorbates like A=H, Se, Xe on (100) or (111) surfaces of bcc or ccp metals and related compounds like hcp metals, NaCl or ZnS form a square, hexagonal, honeycomb or Kagomé net. The ordered structures can be characterized by the self-coordination numbers of nearest, next-nearest and third neighbors T1, T2, T3 and the T1, T2 values plotted in structure maps for a constant ratio of vacant/occupied sites. Most experimental structures have a single coordination of all A atoms. The interactions between A atoms are attractive for chains of A atoms with T1=2 and repulsive for T1=0 or T1=T2=0. The structures with intermediate T1, T2 values can be characterized by sequences of structural units like squares or hexagons with a different occupation of the corners by A atoms.