NONUNIVERSALITY AND BREAKDOWN OF SCALING IN 2-SPECIES AGGREGATION WITH ANNIHILATION

We study the kinetics of a simple model of aggregation with two distin ct monomeric species in which irreversible bonding occurs only between like species and annihilation occurs between unlike species. In the m ean-field approximation we find an unexpected kinetic behaviour which depends crucially on the ratio of reaction rates. For a relatively sim ple model of constant reaction rates, we investigate the corresponding rate equations and derive exact expressions for the exponents describ ing the kinetics of the model. It is observed that the kinetic behavio urs of distinct species are quite different and that corresponding sca ling exponents are also generally nonuniversal. Analytical solutions o f the rate equations show that a modified scaling description, with di fferent sets of exponents for light and heavy species, exists in syste ms with sufficiently weak annihilation; in systems with strong annihil ation, the scaling for the cluster-mass distribution of the light spec ies completely breaks down. A model with constant reaction rates of fu sion and sum-kernel reaction rates of annihilation is also studied.