Damage at a tungsten surface induced by impacts of self-atoms

We study evolution of the surface defects of a 300 K tungsten surface due to the cumulative impact of 0.25-10 keV self-atoms. The simulation is performed by molecular dynamics with bond-order Tersoffform potentials. At all studied impact energies the computation shows strong defect-recombination effect of both created Frenkel pairs as well as recombination of the implanted atoms with the vacancies created by the sputtering. This leads to a saturation of the cumulative count of vacancies, evident at energies below 2 keV, as long as the implantation per impact atom exceeds sputtering and to a saturation of the interstitial count when production of the sputtered particles per impact atom becomes larger than 1 (in the energy range 2-4 keV). The number of cumulative defects is fitted as functions of impact fluence and energy, enabling their analytical extrapolation outside the studied range of parameters. (C) 2015 Elsevier B.V. All rights reserved.