Hydrogen diffusion in Laves-phase compounds

This paper presents a brief review of experimental studies of the mechanisms and parameters of hydrogen diffusion in Laves-phase compounds. Recent progress in understanding of the microscopic picture of hydrogen jump motion in cubic Laves phases is emphasized. Two types of hydrogen jump motion with different characteristic frequencies have been found to coexist in these materials. While the slower jump process is responsible for the long-range diffusion, the faster process corresponds to localized hydrogen motion over small groups of interstitial sites. In some of the Laves-phase compounds, the localized hydrogen motion is not 'frozen out' on the frequency scale of 10(7) - 10(8) s(-1) down to 20 K.