Computer simulation study of the displacement threshold-energy surface in Cu

Computer simulations were performed using the molecular-dynamics technique to determine the directional dependence of the threshold energy for production of stable Frenkel pairs in copper. Sharp peaks were observed in the simulated threshold energy surface in between the low-index directions. Threshold energies ranged from ∼25 eV for directions near $〈100〉$ or $〈110〉$ to 180 eV at the position of the peak between $〈110〉$ and $〈111〉$. The general topographical features of the simulated threshold-energy surface are in good agreement with those determined from an analysis of recent experiments by King et al. on the basis of a Frenkel-pair resistivity ${\rho }_F=2.85\mathrm{}\times {10}^{-4\mathrm{}}$ Ω cm. Evidence is presented in favor of this number as opposed to the usually assumed value, ${\rho }_F=2.00\mathrm{}\times {10}^{-4\mathrm{}}$ Ω cm. The energy dependence of defect production in a number of directions was investigated to determine the importance of nonproductive events above threshold.