Temperature-dependent dissolution and diffusion of H isotopes in iron for nuclear energy applications: First-principles and vibration spectrum predictions

The dissolution and diffusion of H isotopes in bcc-Fe are fundamental and essential parameters in the H energy application from nuclear conversion, whereas the relevant data are lacking and relatively dispersive, demonstrating some important factors have been missed during the past studies. Here, we carry out first-principles total energy and vibration spectrum calculations to investigate systematically the interstitial H dissolution and diffusion behaviors in bcc-Fe by considering the temperature effect. Temperature and H chemical potential are two important factors to affect the H dissolution property. In the interstitial lattice, the H dissolution energy referring to the static/temperature-dependent H chemical potential decreases/increases with the increasing temperature. The diffusion activation energy and pre-factor of H also depend on the temperature and increase significantly with the increasing temperature from 300 to 1000 K. The temperature-correction can give a reasonable interpretation for the broad disseminating in the experimental data of H diffusivity in bcc-Fe. Our currently calculated results reveal that phonon vibration energy plays a crucial role in the H dissolution and diffusion with the increasing temperature.