Quantum mechanical calculation of diffusion of hydrogen isotopes in vanadium

摘要

Diffusion of hydrogen isotopes in vanadium was investigated by a quantum mechanical calculation. Wave functions and the corresponding eigen energies (ξ) for hydrogen isotopes were obtained as a function of hydrogen position along the diffusion path (ξ) by solving the three dimensional Schrodinger equation. Hydrogen potential was calculated by using a first principles method with a nudged elastic band technique. By analyzing the E-ξ curves, the tunneling matrix elements were obtained for the coincidence states between two neighboring tetrahedral sites. It was clarified that the tunneling between ground states was dominant at low temperatures, whereas the contribution of that between the first exited states becomes larger at higher temperatures. The transition temperature of the dominant tunneling decreases with the isotope mass. The calculated temperature dependence of the diffusion for the V-H system quantitatively agreed with the experimental data in the literature, although those for the V-D and -T systems were somewhat underestimated.