Hydrogen Transport in Tungsten for Nuclear Energy Application: Temperature Dependence and Compensation Effect

We performed systematically first-principles calculations to investigate interstitial H diffusion/permeation of temperature dependence in tungsten (W). The interstitial H diffusion is primarily through two nearest-neighbor tetrahedral positions and its activation energy increases significantly with rising temperature. Phonon vibration plays a decisive role in the behavior of the H activation energy with rising temperature. The H permeation activation energy also depends strongly on the temperature since it is the sum of the formation energy and diffusion activation energy of H. Our calculated H diffusivity/permeability with the temperature agree quantitatively with the reliable experimental data within the error range in W. The vacancy-capturing effect can give a reasonable explanation of the discrepancy between simulation and experiment. Although the diffusion/permeation activation energy and the prefactor strongly depend on the temperature, the diffusivity/permeability of H still obeys quasi-Arrhenius behavior with rising temperature, which is attributed to the compensation effect between the activation energy and the prefactor, i.e., the increment of the prefactor compensates directly the modification of the diffusivity/permeability in the case of a variation in the activation energy with rising temperature.