Particle adsorption on finite-width square terraces in stepped surfaces

The preferential adsorption on the steps of finite-width terraces is modeled by allowing lattice–adsorbate interaction at the edges (or steps) of the terrace to be different from that in the bulk. As in our previous studies, the system is at sufficiently low temperature, and at thermodynamic equilibrium. However, no a priori assumptions are made as to whether forces are attractive or repulsive, or as to their relative strength. The occupational characteristics of all the phases are found to fit exact analytic expressions in the width M of the terrace. Many numerical values of the occupational characteristics at the transitions also fit exact analytic expressions in M and the golden ratio (1+(5)1/2)/2. Our results are compared with experiments, in particular, the adsorption of cobalt on Ag(1 0 0), and bromine on Cu(s)-[10(1 0 0)×1(0 0 1)].