High temperature adsorption isotherms on equilateral triangular terraces

Within the context of a lattice–gas model, the adsorption isotherms on infinitely long equilateral triangular terraces are obtained at high temperature using a recently developed transfer matrix method. The computations, using long double precision arithmetic, are conducted for semi-infinite terraces with two different orientations, an increasing number M of atomic sites in their width, and without a periodic boundary. Our general formulation recovers the known results of the statistical average of the coverage and the entropy per site divided by Boltzmann's constant, which is independent of M   and given by the one-dimensional solution (M=1M=1). We report as new results the values of θ(M,θ0)θ(M,θ0) and β(M,θ0)β(M,θ0), which are the statistical averages of the numbers of first- and second-neighbors per site, respectively, as functions of the width M   and the coverage θ0θ0. These functions, when scaled according to their maximum values obtained at full coverage, both reduce to θ02 for all M. With this new information, we show that in the infinite-M limit, and at half coverage, the adsorbate occupational configuration exhibits repetitive hexagonal patterns.