Hydrogen diffusion in the metallic glass a-Zr3RhH3.5

A series of NMR experiments has been conducted on ${}_{}{}^1{}_{}{}^{}\mathrm{H}$ in the metallic glass a-${\mathrm{Zr}}_3$ ${\mathrm{RhH}}_{3.5}$ to establish the temperature dependence of the mean H-atom jump rate. Temperature and frequency dependence of the ${}_{}{}^1{}_{}{}^{}\mathrm{H}$ spin-lattice relaxation rates and, at three temperatures, the H-atom translational (tracer) diffusion coefficient D have been measured. The pulsed-field-gradient, stimulated-echo technique was used to measure D. At 525 K, D=3.9×${10}^{\mathrm{-}7}$ ${\mathrm{cm}}^2$/s. Atomic jump rates deduced from D measurements are consistent with those calculated from relaxation-rate data, indicating that translational diffusion is responsible for ${}_{}{}^1{}_{}{}^{}\mathrm{H}$ spin-lattice relaxation. It is demonstrated that a distribution of activation energies about a mean energy, E${¯}_a$=0.46 eV/atom, is needed to fit relaxation-rate data. The width, 0.12 eV, and the mean energy of the distribution are independent of temperature. A procedure is suggested for using NMR measurements to establish the existence of a distribution of activation energies for atomic motion.