A general expression was proposed for the chemical diffusion coefficient of H in disordered alloys. This took account of the non-equivalence of interstitial sites in the alloys; due to differences in their nearest-neighbor surroundings. Determination of the diffusion coefficient was shown to reduce to the calculation of a sum over various atomic configurations that contained the probabilities of individual jumps between the adjacent interstitial sites. This sum was shown to determine the dependence of the diffusion coefficient upon the alloy composition and H concentration.

V.V.Kondratev, A.N.Voloshinskii, A.G.Obukhove: Physics of Metals and Metallography, 1996, 81[2], 124-30