Monte-Carlo simulations of chemical reactions in molecular crystals

Chemical reactions in molecular crystals, yielding new entities (dimers, tr imers,..., polymers) in the original structure, are simulated for the first time by stochastic Monte Carlo methods. The results are compared with thos e obtained by deterministic methods. They show that numerical simulation is a tool for understanding the evolution of these mixed systems. They are in kinetic and not in thermodynamic control. Reactive site distributions, x-r ay diffuse scattering, and chain length distributions can be simulated. Com parisons are made with deterministic models and experimental results obtain ed in the case of the solid state dimerization of cinnamic acid in the beta phase and in the case of the solid state polymerization of diacetylenes. ( C) 1999 American Institute of Physics. [S0021-9606(99)51202-6].