On the calculation of atomic displacements using damage energy

Abstract

The present work investigates the discrepancy between the numbers of atomic displacements from the direct computation and the damage energy-based calculation in Full Cascade (FC) simulation of SRIM-like codes. A new formula of atomic displacements is proposed to correlate the atomic displacements and damage energy. The efficiency of displacement increases with ion energy below keV owing to the increase of residual energy transfer efficiency. In general, the number of atomic displacements is proportional to the damage energy for incident ion energy above keV and about 2 times the value deduced from the modified Kinchin-Pease formula. The linear relationship between atomic displacement and damage energy should also be valid for neutron-induced irradiation damage in operating nuclear reactors due to high neutron energy. Based on the proposed formula, the ratio of damage between Quick Calculation (QC) and FC is then deduced with a unique parameter correlating the number of vacancies and damage energy. Using the approximate value 0.86 from binary collision approximation to correct atomic scattering, the reference value of FC/QC is FC/QC0=2.15. It is observed that FC/QC’s of total atomic vacancies are well included in [0.9, 1.2]×FC/QC0.