Evaluation of the threshold displacement energy in tungsten by molecular dynamics calculations

The threshold displacement energy (TDE) is an important quantity used to determine the number of defects formed by irradiation of high-energy particles. For the TDE of tungsten, different values have been reported and then used in previous studies, which has caused inconsistencies in calculated damage amounts. In the present study, we evaluate the TDE using molecular dynamics calculations, where the TDE is defined as the average value of the minimum displacement energies for creating a stable defect over all recoil directions. To determine the TDE accurately, the effects of calculation settings, such as the simulation cell size, the number of sampled recoil directions, the increment step of the recoil energy in searching the threshold value, and the thermal vibration of atoms, were analyzed. A TDE of 85 eV was obtained for tungsten with an estimated error of 4.5%. This TDE value is close to the one recommended by the American Society for Testing and Materials (ASTM), 90 eV. Consequently, we conclude that 90 eV is a reasonable choice for the TDE of tungsten.