Localized hydrogen motion in C15-type TaV2H0.65: temperature dependence of the H jump rate

摘要

In order to study the temperature dependence of the jump rate tau(-1)(l) l for the fast localized motion of hydrogen in cubic (C15-type) Laves-phase TaV2, we have performed time-of-flight quasielastic neutron scattering measurements for TaV2H0.65 over the temperature range 12-290 K. The quasielastic line broadening corresponding to the localized H motion has been observed down to 70 K; the observability of the quasielastic line at lower temperatures is limited by the decrease in the fraction of H atoms participating in the fast localized motion. In the range 70-290 K the temperature dependence of tau(-1)(l) is found to deviate from the Arrhenius behaviour. This temperature dependence can be reasonably well described by the exponential function exp(T/T-0) with T-0 = 220 K. The same function with T-0 of the order of 100 K also appears to describe tau(-1)(l)(T) in some other metallic systems showing fast localized hydrogen motion.