Multistability of steady states in competitive adsorption of two species

摘要

Competitive adsorption of two species on a linear chain is considered. The adsorptionndash;desorption probabilities are chosen in the Arrhenius form and it is assumed that the activation energies are partially due to interaction between nearest neighboring adatoms. Multistability can occur for an attractive interaction greater than a critical value, depending on the values of other parameters, and the least critical value corresponding to an interaction energy of bartil;0.3 kcalthinsp;molminus;1for room temperature. Up to seven steady states can result, three being stable. The relaxation times tend to infinitum at the critical points and the exponent agr;, where tgr;Jrarr;Jcriticalsim;(Jcriticalminus;J)minus;agr;andJbeing a parameter gauging the strength of the interaction, has been determined for a number of cases. The analysis has been extended to twohyphen;dimensional lattices and similar results have been obtained, althoughJcriticalis less than that for the linear chain. Next a dimerization reaction between adatoms has been considered jointly with the adsorptionndash;desorption process. The results obtained are again similar to the previous ones. It is noteworthy that when three stable steady states exist, depending on initial conditions, two of these states correspond to cases where one of the type of the adatoms has saturated the surface, thus displacing the other species, and practically stopping the dimerization reaction. The third state corresponds to partial coverages of the surface for both types of adatoms and the reaction rate is greater.