The permeation and diffusion of H through membranes of 4N-purity material were studied by using time-lag methods. The diffusion coefficients which were deduced in this way were associated with an activation energy that was much lower than those previously determined. A survey of published diffusion data (figure 13) suggested that the activation energy for H diffusion should be about 0.1eV for body-centered cubic metals and between 0.3 and 0.6eV for face-centered cubic metals. The pressure- and temperature-dependences of the permeability could be described by empirical relationships. Diffusivity and Permeability of Hydrogen in Molybdenum. H.Katsuta, R.B.McLellan, K.Furukawa: Journal of Physics and Chemistry of Solids, 1982, 43[6], 533-8