, P.H. Kien1*, P.K. Hung1, and V.V. Hung2, 1, Department of Computational Physics, Hanoi University of Technology, 2, Department of Physics, Hanoi University of Education, ABSTRACT, The boron concentration dependence of the microscopic bubbles for the amorphous alloys, (AMAs) FexB100-x with x = 70, 75, 80, 85 and 90 has been investigated by statistical relaxation, method. The larger number of microscopic bubbles has found in AMAs. The simulation result, shows the vacancy bubbles in the AMAs vary in a range 0.9 x 10-2, -1.6 x 10-2, bubble per atom, depending on the concentration of boron atoms. The vacancy bubbles could play a role of, diffusion vehicle for cobalt atom. The number of vacancy bubbles decreased on decreasing of, boron concentration. A new diffusion mechanism for tracer diffusivity in AMAs as follow: The, elemental atomic movement includes a jump of neighboring atom into the vacancy-bubbles and, then collective displacement of a large number of atoms. The diffusion coefficient of iron and, boron atoms are also determined and discussed here.