Computer simulation studies of recombination of ions in multi ion-pair ensembles—I. Diffusion-controlled processes

• Published in: Computers & chemistry 1998-01, Vol.22 (1), p.71-78
• Main Authors: Bartczak, Witold M, Wolf, Krystyna, Hummel, Andries
• Format: Article
• Language: English
• ISSN: 0097-8485
• DOI: 10.1016/S0097-8485(97)00052-1

The problem of the diffusion-controlled recombination of ions for the case in which initially two or more non-separable pairs of oppositely charged ions are present in the system is treated by means of a computer simulation method. In the first part of the project, the calculations were performed for the media with the short mean free path of the free movement of ions between scattering events, i.e. for the conditions of the diffusion model of the ion transport. The movement of an ion is simulated by a superposition of random walk and drift in the electric field of all the other ions in the system. Thus, the calculations belong to the class of stochastic dynamics methods. The simulations assumed the partition of an ion ensemble into small independent clusters of up to ten ion pairs. Results were obtained on the probability of ion survival as a function of time and the probability of ion escape from recombination at infinite time. The scale of the deviations of the kinetics of the recombination process in the multi-pair clusters from the kinetics for the isolated pairs was estimated. Another series of the computer experiments simulate diffusion-controlled recombination (annihilation) of ions in model supersaturated solutions with different concentrations of ionic solutes and different dielectric constant of the solutions. The simulations yield the ion survival probability as a function of time and allow us to calculate the rate constant of the ion recombination as a function of the ion concentration.