Interactions between chemisorbed atoms: Oxygen on W(110)

Experimental LEED data on the 2×1 structure formed on W(110) by oxygen adsorption at coverages ϑ?0.5 are computer simulated by means of the Monte Carlo technique in terms of interactions between nearest and next-nearest neighbor adsorbed atoms. A minimum set of three (properly chosen) interaction energies was found to yield good agreement with experimental results, i.e., the variation of the relative intensity and angular width of the half-order overlayer beams with temperature and coverage. The pairwise interactions are of oscillatory character (i.e., changing sign from repulsive to attractive), have energies in the order of 1 kcal/mole, and fall off within 1–2 lattice spacings. They thus exhibit all the qualitative criteria of indirect interactions between adatoms as treated theoretically in the literature.