Accession Number : ADA180261

Title :   Comparison of the Rates of Uni- and Bi-Molecular Diffusion Controlled Reactions on Circular, Filled Aggregate and DLA Fractal Aggregate in Two Dimensions.

Descriptive Note : Technical rept.,

Corporate Author : CALIFORNIA UNIV LOS ANGELES DEPT OF CHEMISTRY AND BIOCHEMISTRY

Personal Author(s) : Yang,Chan-Lon ; Chen,Zhong-Ying ; El-Sayed,Mostafa A

PDF Url : ADA180261

Report Date : 07 May 1987

Pagination or Media Count : 29

Abstract : The effects of irregular, open structures of two dimensional aggregates on the rates of diffusion controlled reactions are examined by computer simulation. The simulation model describes the reaction between two species, A and B, where A is randomly distributed on a two dimensional square lattice and diffuses like a random walker while B forms a fixed aggregate of different shapes and sizes. Both unimolecular (i.e., B is non-destructive but A disappears upon reaction) and bimolecular (i.e., both A and B disappear after the reaction) mechanisms are examined. Different sizes of DLA aggregates are chosen to model the irregular aggregates and to compare the reaction rates with the circular, compact aggregates of different radii. For unimolecular reaction, with the same total mass, the DLA aggregate shows a faster reaction rate than the circular one for its open structure. In the bimolecular mechanism, the sizes (or radii) of the aggregates decrease during reaction processes, and the reaction rate is slower compared to the unimolecular reaction. This shrinkage effect is more distinct for DLA aggregates than the compact aggregates. Keywords: Fractals, Kinetics, Diffusion, Aggregation, Surface diffusion.

Descriptors :   *MOLECULES, *DIFFUSION, *REACTION KINETICS, COMPUTERIZED SIMULATION, RATES, REACTION TIME, STRUCTURES, SHRINKAGE, COMPARISON, CONTROL, FILLING, RESPONSE, MODELS, SIMULATION, SURFACES, TWO DIMENSIONAL, REACTANTS(CHEMISTRY), PARTICLE SIZE, SURFACE REACTIONS, SHAPE

Subject Categories : Physical Chemistry

Distribution Statement : APPROVED FOR PUBLIC RELEASE