The simulation finds a large number of vacancy-simplexes, which plays a role of diffusion vehicle for cobalt atom and varies with relaxation degree. A new diffusion mechanism for tracer diffusivity in cobalt amorphous solid is supposed as follows: The elemental atomic movement includes a jump of neighbouring atoms into the vacancy-simplexes and then collective displacement of a large number of atoms. | JOURNAL OF SCIENCE OF HNUE Natural Sci. 2010 Vol. 55 No. 6 pp. 28-36 SIMULATION STUDY OF TRACER SELF-DIFFUSION MECHANISM IN COBALT AMORPHOUS SOLIDS Pham Huu Kien and Pham Khac Hung Hanoi University of Science and Technology Vu Van Hung Hanoi National University of Education E-mail huukienpham@ statistical relaxation SR simulation has been conducted to study the behavior of simplexes in cobalt amorphous solid containing 2 105 atoms. The simulation reveals that the fraction of 4-simplex increases and of N-simplex with N gt 4 decreases upon relaxation degree. The simulation finds a large number of vacancy-simplexes which plays a role of diffusion vehicle for cobalt atom and varies with relaxation degree. A new diffusion mechanism for tracer diffusivity in cobalt amorphous solid is supposed as follows The elemental atomic movement includes a jump of neighbouring atoms into the vacancy-simplexes and then collective displacement of a large number of atoms. Keywords Amorphous solid Microscopic bubble Vacancy-simplex Diffu- sion mechanism Statistical relaxation Molecular dynamic. 1. Introduction Metal has been known as an indispensable material in the lives of the whole of mankind. So it has attracted the attention of many researchers in all fields ex- periments theory and computer simulation 1-10 . In all of the nature of the metal atom diffusion mechanism in amorphous metals AM is the topical area of high nature and should be particularly interesting to research. Many works have studied the atomic diffusion mechanisms in amorphous solids 1 8 9 . For example the ex- perimental researches 4-7 said that in amorphous solids there exists quasi-vacancy and diffusion mechanism of the atom is indirect through quasi-vacancy. However the definition of quasi-vacancy is still not well understood and is not a question to be answered. On the other hand computer simulation has proved the existence of the vacancy in amorphous solids 1 2 8 the number of vacancies .
