Structure Maps Of Surface Structures

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 neighborsT1,T2,T3and theT1,T2values 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 withT1=2and repulsive forT1=0orT1=T2=0. The structures with intermediateT1,T2values can be characterized by sequences of structural units like squares or hexagons with a different occupation of the corners by A atoms.