First-principles investigation of diffusion behaviours of H isotopes:From W(110) surface into bulk and in bulk W

摘要

The diffusion behaviours of hydrogen（H）,deuterium（D）,and tritium（T） from W（110） surface into bulk and in bulk W are investigated using first-principles calculations combined with simplified models.The diffusion energy barrier is shown to be 1.87 eV from W（110） surface to the subsurface,along with a much reduced barrier of 0.06 eV for the reverse diffusion process.After H enters into the bulk,its diffusion energy barrier with quantum correction is 0.19 eV. In terms of the diffusion theory presented by Wert and Zener,the diffusion pre-exponential factor of H is calculated to be 1.57×10-7 m2·s-1,and it is quantitatively in agreement with the experimental value of 4.1×10-7 m2·s-1. Subsequently,according to mass dependence(（1/m）1/2) of H isotope effect,the diffusion pre-exponential factors of D and T are estimated to be 1.11×10-7 m2·s-1 and 0.91×10-7 m2·s-1,respectively.