Simulations based upon a semi-empirical quantum model were performed to examine the diffusion of hydrogen in a dense nickel membrane. The mean square displacement and diffusion coefficients of the nickel and hydrogen atoms were derived at 300 to 1800K. The numerical results revealed the changes which took place in the transportation mechanism of the hydrogen atoms as a result of a temperature-induced variation in the lattice structure. It was shown that the transport of the hydrogen atoms changed from an interstitial diffusion mechanism at below 1200K to a vacancy diffusion mechanism at 1600 to 1800K, as a result of a change in the nickel lattice from an ordered face-centered cubic structure to an amorphous-type structure.

Numerical Simulation of Hydrogen Atom Transport in Thick Nickel Membrane using Semi-Empirical Quantum Model. Chen, B.H., Chuang, C.H., Ahluwalia, R.K., Chang, M.L.: International Journal of Hydrogen Energy, 2009, 34[24], 9824-31