The transport characteristics of hydrogen atoms are of significant interest within the energy industry. in this study, molecular dynamics (MD) simulations based on a semi-empirical quantum model are performed to examine the diffusion of hydrogen in a dense nickel membrane. The mean square displacement (MSD) and diffusion coefficients of the nickel and hydrogen atoms are derived at various temperatures in the range of 300-1800 K. The numerical results reveal the changes which take place in the transportation mechanism of the hydrogen atoms as a result of a temperature-induced variation in the lattice structure. It is shown that the transport of the hydrogen atoms changes from an interstitial diffusion mechanism at temperatures lower than 1200 K to a vacancy diffusion mechanism at temperatures of 1600-1800 K as result of a change in the nickel lattice from an ordered FCC structure to an amorphous-type structure. (C) 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.