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

TL;DR

This study uses first-principles calculations and transition state theory to predict how hydrogen, deuterium, and tritium diffuse in alpha-titanium across various temperatures, aligning well with experimental data.

Contribution

It introduces a comprehensive first-principles approach to calculate temperature-dependent diffusion coefficients for hydrogen isotopes in alpha-titanium, considering multiple diffusion paths and impurity occupancy states.

Findings

Deuterium and tritium diffuse more slowly than hydrogen above certain temperatures.

Calculated diffusion coefficients agree well with experimental measurements.

Diffusion rates vary with temperature and isotope type.

Abstract

We report the prediction of temperature-dependent diffusion coefficients of interstitial hydrogen, deuterium, and tritium atoms in $\alpha$-Ti using transition state theory. The microscopic parameters in the pre-factor and activation energy of the impurity diffusion coefficients are obtained from first-principles total energy and phonon calculations including the full coupling between the vibrational modes of the diffusing atom with the host lattice. The dual occupancy case of impurity atom in the hcp matrix are considered, and four diffusion paths are combined to obtain the final diffusion coefficients. The calculated diffusion parameters show good agreement with experiments. Our numerical results indicate that the diffusions of deuterium and tritium atoms are slower than that of the hydrogen atom at temperatures above 425 K and 390 K, respectively.