Kinetic phase transitions in dimer-dimer irreversible catalytic surface reactions of the type: A(2)+xB(2)-> 2AB(x)

The kinetics of irreversible dimer-dimer surface reactions of the type A(2) + xB(2) --> 2AB(x) (x takes values 1, 2 and 3), with desorption of dimer B -2, has been investigated by means of Monte Carlo simulation. For a desorpt ion probability (P) of B-2 equal to zero, a single discontinuous transition separating one saturated state from another is obtained at a point where f eed concentration is exactly related to the stoichiometry of the particular reaction. With the increase in P, a steady reactive state which is separat ed from the poisoned states by two transitions is obtained for each reactio n scheme. The position of the transition points depends upon the value of P . For P equal to one, a single continuous transition point separates a pois oned state from a steady reactive state for each reaction scheme. The windo w width, which defines the steady reactive state, shows an exponential beha viour with P. (C) 1999 Elsevier Science B.V. All rights reserved.