Kinetic phase transitions in the A-B2-D surface reaction model

Abstract

A monomer-dimer-monomer (A-B2-D) lattice surface reaction model is proposed, in which two adsorption parameters XA and XD are involved. The phase diagram for this model is determined by the partial simulation method. For the case of no desorption being considered, six phases are found, which are the two-species saturated phases SAD, SBD, SBE and SAE (E denotes the intermediate product AB), the one-species saturated phase SB and the steady reactive phase R. The R and SB phases are restricted to the line XA=XD. Phase transitions between two-species phases or between R and SB are all second order, while that between R and SAD is first order. It appears that there exists a pentacritical point at XA=XD=0.023+or-0.001. If D* desorption is taken into account, the reactive phase R extends to a region of finite area.