First-principles study of temperature-dependent diffusion coefficients: Hydrogen, deuterium, and tritium in $\alpha$-Ti

摘要

We report the prediction of temperature-dependent diffusion coefficients ofinterstitial hydrogen, deuterium, and tritium atoms in $\alpha$-Ti usingtransition state theory. The microscopic parameters in the pre-factor andactivation energy of the impurity diffusion coefficients are obtained fromfirst-principles total energy and phonon calculations including the fullcoupling between the vibrational modes of the diffusing atom with the hostlattice. The dual occupancy case of impurity atom in the hcp matrix areconsidered, and four diffusion paths are combined to obtain the final diffusioncoefficients. The calculated diffusion parameters show good agreement withexperiments. Our numerical results indicate that the diffusions of deuteriumand tritium atoms are slower than that of the hydrogen atom at temperaturesabove 425 K and 390 K, respectively.