Irradiation damage of helium-accumulated vanadium: atomic simulations

Abstract

Molecular dynamics simulations have been implemented to gain insight into the displacement cascades in vanadium containing substitutional He atoms with several different concentrations from 0.2 to 1.0 at%. The dependence of displacement cascades on the irradiation temperature (300 and 600 K) and energy of the primary knock-on atom (from 5 to 40 keV) have been analysed. It was shown that the number of Frenkel pairs increases with the increase of the energy of the primary knock-on atom. The increasing rate of the number of Frenkel pairs at 600 K is lower than that at 300 K. The predominant attention has been focused on the formation of He-vacancy clusters. The obtained results show that the number of He-vacancy clusters increases with the increase in He concentration and the energy of the primary knock-on atom. The largest size of He-vacancy is independent on the energy of the primary knock-on atom and the irradiation temperature at low He concentrations. The configurations of small He-vacancy clusters are different from those in iron. The He atoms in He-vacancy clusters prefer to occupy the tetrahedral interstitial sites rather than the octahedral interstitial sites.