Molecular-dynamics studies of annihilation reactions

F. Baras; M. Salazar; E. Kestemont; M. Malek Mansour

doi:doi:10.1209/epl/i2004-10143-4

Europhys. Lett., 67 (6), pp. 900-906 (2004)
DOI: 10.1209/epl/i2004-10143-4

Molecular-dynamics studies of annihilation reactions

F. Baras¹, M. Salazar¹, E. Kestemont² and M. Malek Mansour²

¹ Laboratoire de Recherches sur la Réactivité des Solides UMR 5613 CNRS-Université de Bourgogne 9 Avenue Alain Savary - BP 47870, F-21078 Dijon Cedex, France
² Centre for Nonlinear Phenomena and Complex Systems Université Libre de Bruxelles, Campus Plaine - C.P. 231, B-1050 Brussels, Belgium

(Received 14 April 2004; accepted in final form 8 July 2004)

Abstract
The validity of the reaction-diffusion formulation of annihilation kinetics, with randomly distributed initial conditions, is investigated by molecular-dynamics simulations of dense hard-disk fluids. For the reaction $A+B\rightarrow C+C$ quantitative agreement is found. Yet, this proves not to be the case for the reaction $A+A\rightarrow C+C$ , where major discrepancies are observed. For this latter reaction, more sophisticated theories predict a logarithmic decay law of the form $\ln(t)/t$ . The microscopic simulations essentially confirm this prediction.

PACS
05.40.-a - Fluctuation phenomena, random processes, noise, and Brownian motion.
05.90.+m - Other topics in statistical physics, thermodynamics, and nonlinear dynamical systems.
82.20.Wt - Computational modeling; simulation.

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