Employing a first-principles method, an investigation was made of dissolution and diffusion properties of hydrogen in molybdenum. It was shown that single H atom was energetically favorable sitting at the tetrahedral interstitial site instead of octahedral interstitial site and diagonal interstitial site. This could be confirmed by the electron localization function result. Bader charge analysis suggested that the bonding between H and surrounding Mo was mainly ionic mixed with slight covalent component. Double H atoms tend to be paired up at the two neighboring tetrahedral interstitial sites along the <110> direction with the distance of about 0.221nm and the binding energy of 0.03eV. This suggested a weak attractive interaction between H atoms, with the implication that self-trapping of H and thus formation of the H2 molecules were quite difficult in an intrinsic Mo environment. It was demonstrated that the diffusion barrier of H that jumps between the tetrahedral interstitial sites was 0.16eV, and the dissolved concentration of H in the intrinsic Mo was 2.6 x 10−8 at a typical temperature of 600K. The diffusion coefficients of H, D and T were different due to the different masses, which were calculated to be 1.3 x 10−7, 9.2 x 10−8 and 7.5 x 10−8m2/s at 600K.

First-Principles Study on Dissolution and Diffusion Properties of Hydrogen in Molybdenum. C.Duan, Y.L.Liu, H.B.Zhou, Y.Zhang, S.Jin, G.H.Lu, G.N.Luo: Journal of Nuclear Materials, 2010, 404[2], 109-15