Molecular dynamics simulation of vacancy diffusion in tungsten induced by irradiation

Abstract

Influence of irradiation with sub-threshold energy on vacancy diffusion, which is not usually considered in the radiation effect, was investigated by molecular dynamics simulation. The displacement threshold energy, E d, has been investigated in tungsten. It depends strongly on orientation, and the minimum E d is 68 ± 0.5 eV in the 〈1 0 0〉 direction. The recoil energies for vacancy migration also depend strongly on the orientation, and they are 1.9, 9.4 and 52.9 eV in the 〈1 1 1〉, 〈1 0 0〉 and 〈1 1 0〉 directions, respectively. The average recoil energy for a vacancy migration is estimated to be 3.1 ± 0.05 eV. This means that vacancy diffusion is enhanced by irradiation even in the low energy range which is less than the displacement threshold energy. In addition, the recoil atom interacts with not only the nearest-neighbor vacancies, but also distant vacancies. The long distance interaction between the recoil atom and a vacancy is prominent in the 〈1 1 1〉 direction.