Critical behavior of repulsively interacting particles adsorbed on disordered triangular lattices

• Published in: Physical chemistry chemical physics : PCCP 2010-01, Vol.12 (4), p.1328-13286
• Main Authors: Perarnau, M. A, Centres, P. M, Bulnes, F, Ramirez-Pastor, A. J
• Format: Article
• Language: English
• Subjects: Chemistry; Exact sciences and technology; General and physical chemistry; Surface physical chemistry
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c003983g

A simple model for amorphous solids, consisting of a triangular lattice with a fraction of attenuated bonds randomly distributed (which simulate the presence of defects in the surface), is used here to find out, by using grand canonical Monte Carlo simulations, how the adsorption thermodynamics of repulsively interacting monomers is modified with respect to the same process in the regular lattice. The degree of disorder of the surface is tunable by selecting the values of (1) the fraction of attenuated bonds ρ (0 ≤ ρ ≤ 1) and (2) the attenuation factor r (0 ≤ r ≤ 1), where r is defined as the ratio between the value of the lateral interaction associated to an attenuated bond and that corresponding to a regular bond. Adsorption isotherm and differential heat of adsorption calculations have been carried out showing and interpreting the effects of the disorder. A rich variety of behavior has been observed for different values of ρ and r , varying between two limit cases: bond-diluted lattices ( r = 0 and ρ ≠ 0) and regular lattices ( r = 1 and any value of ρ ). In addition, the critical behavior of the system was studied, showing that the order-disorder phase transition observed for the regular lattice survives, though with modifications, above a critical curve ( ρ - r -temperature). Even though the presence of defects affects the formation of ordered structures in the adlayer, the phase transition survives up to a certain critical degree of disorder.