Three-State Lattice Gas on a Triangular Lattice as a Model for
Multicomponent Adsorption
P. A. Rikvold, J. B. Collins, G. D. Hansen,
and J. D. Gunton
Surf. Sci. 203, 500-524 (1988)
Abstract
We consider a three-state lattice gas with nearest-neighbour
interactions on a triangular lattice as a model
for multicomponent chemi- and physisorption. By varying the
lateral interaction constants between the adsorbate
particles, this model can be made to exhibit either enhanced
adsorption or poisoning (inhibited adsorption). Following a
ground-state calculation and a discussion of the conditions
on the interaction constants that lead to enhanced
adsorption and poisoning, we calculate phase diagrams and
adsorption isotherms by the finite-size scaling transfer-matrix
method. Detailed numerical studies of the phase
diagrams are performed for two models, one that exhibits
enhanced adsorption, and one that exhibits poisoning.
Finally we consider a simple model for the coadsorption of
hydrogen and sulphur on a platinum (111) surface, with
interaction constants estimated from experimental results.
The resulting adsorption isotherms are in good agreement
with experimental results. We find that transfer-matrix
calculations provide an efficient method for obtaining
adsorption isotherms for complicated systems with a
surprisingly modest computational effort.