tailieunhanh - A study of diffusion in a disordered chain: Computer simulation

Using the non-force method we simulate diffusion on a disordered chain consisting of 2000 sites for a wide range of temperature. Three types of disordered chains, site, saddle and site-saddle system are considered. The influence of site and saddle disorders and Arrhenius behavior is also investigated and discussed in this work. | JOURNAL OF SCIENCE OF HNUE Mathematical and Physical Sci. 2012 Vol. 57 No. 7 pp. 142-150 This paper is available online at http A STUDY OF DIFFUSION IN A DISORDERED CHAIN COMPUTER SIMULATION Trinh Van Mung1 Pham Khac Hung2 and Nguyen Thi Thanh Ha2 1 Vinh Phuc College Vinh Phuc Province 2 Department of Computational Physics Institute of Engineering Physics Hanoi University of Science amp Technology Abstract. We have examined two simulation techniques for diffusion on disordered systems the non-force and force method. The latter enables one to study diffusion on the system with periodic boundary conditions and size which is 20 times shorter than the non-force method. Furthermore the force method is an appropriate way to study impurity diffusion in a more real model of amorphous solid constructed by molecular dynamic or statistic relaxation techniques. Using the non-force method we simulate diffusion on a disordered chain consisting of 2000 sites for a wide range of temperature. Three types of disordered chains site saddle and site-saddle system are considered. The influence of site and saddle disorders and Arrhenius behavior is also investigated and discussed in this work. Keywords Diffusion random walk disordered system simulation non-force method. 1. Introduction Despite great effort over a long period of time many aspects of diffusion in amorphous alloys AM are still poorly understood 1-3 . For example it is still not clear why the existence of a wide continuous spectrum of site and saddle point energy for diffusion process could also give rise to the Arrhenius behavior experimentally observed in certain AMs 4-6 . In comparison with crystal counterparts the pre-exponential factor as well as activation energy exhibits certain specific features. For instance the factor Do for diffusion of some impurities in AMs changes in the very wide range of 10 7 cm2 s 2-3 . Several models have been suggested to clarify those observations. One the Fisher random