Primary Ion-Irradiation Damage of BCC-Iron Surfaces

Using MD simulations, the influence of crystallographic orientation of an irradiated surface on the evolution of atomic displacement cascades is investigated in BCC-iron. The energy of atomic displacement cascades is varied from 1 to 20 keV. It is found that irradiation of the (111) surface results in crater formation while irradiation of the (110) surface gives rise to the formation of vacancy-type dislocation loops with the Burgers vectors а or a/2 . Both processes are associated with anisotropic propagation of the shock waves generated by the atomic displacement cascades. In the case of low energies of the latter, the number of point defects survived near the (110) surface is larger than that near (111). At higher energies, the influence of the free surface orientation on the number of survived defects decreases.