Adsorption of binary mixtures on two-dimensional triangular lattices

• Published in: Surface science 2020-11, Vol.701, p.121698, Article 121698
• Main Authors: Sanchez-Varretti, F.O., Pasinetti, P.M., Bulnes, F.M., Ramirez-Pastor, A.J.
• Format: Article
• Language: English
• Subjects: Cluster approximation; Equilibrium thermodynamics and statistical mechanics; Gas mixture adsorption; Lattice-gas models; Monte Carlo simulations; Quasi-chemical approximation
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/j.susc.2020.121698

•Interacting binary mixtures adsorbed on triangular lattices were studied.•A lattice-gas model was developed.•The calculations were performed by Monte Carlo (MC), quasi-chemical (QCA) and cluster-exact approximation (CA).•The presence of ordered structures in the adsorbed layer was observed.•An excellent agreement was found between MC and CA.•QCA fails to reproduce the low temperature ordered structures. [Display omitted] The adsorption of interacting binary mixtures on triangular lattices is studied by combining theory and Monte Carlo (MC) simulations. Two theoretical approximations are used in the present work: (i) the cluster approximation (CA), based on exact counting of adsorption states on small lattices; and (ii) an extension of the standard quasi-chemical approximation (QCA) that includes two adsorbed species (a and b). In the case of CA, an own algorithm is developed to obtain the configurational grand partition function for small cells. Repulsive lateral couplings between adsorbate-adsorbate species are incorporated in the lattice-gas framework. Theoretical (CA and QCA) total and partial adsorption isotherms are compared with MC simulations. Quantitative and qualitative differences are shown and discussed, being CA the more accurate approach in all cases.