Hydrogen jump diffusion in C14-typeZrMn2H3: Quasielastic neutron scattering study

Abstract

In order to study the mechanism and parameters of hydrogen diffusion in the hexagonal ͑C14-type͒ Lavesphase ZrMn 2 , we have performed quasielastic neutron scattering measurements for ZrMn 2 H 3 over the temperature range 10-390 K. It is found that the diffusive motion of hydrogen in this system can be described in terms of at least two jump processes: a fast localized H motion with the jump rate l −1 and a slower process with the rate d −1 associated with H jumps leading to long-range diffusion. The temperature dependence of d −1 in the range 225-390 K follows the Arrhenius law with the activation energy of 124± 4 meV. In the same range, the temperature dependence of l −1 deviates from the Arrhenius behavior and is considerably weaker than that of d −1 . The Q dependence of the elastic incoherent structure factor ͑studied up to Q max Ϸ 3.8 Å −1 ͒ suggests that the fast localized H motion in ZrMn 2 H 3 corresponds to two-site jumps within pairs of closely spaced interstitial Zr 2 Mn 2 sites.

Hydrogen Rotational and Translational Diffusion in Calcium Borohydride from Quasielastic Neutron Scattering and DFT Calculations

“…This method is optimal to study hydrogen dynamics because of the large incoherent scattering cross section of hydrogen compared to all other scattering signals . Although the dynamics in interstitial metal hydrides have been widely studied with neutron scattering, − only few published results on complex hydrides exist. As examples, the hydrogen dynamics in NaAlH 4 and Na 3 AlH 6 were studied.…”

Hydrogen dynamics in Ce2Fe17H5: inelastic and quasielastic neutron scattering studies

“…For the measurements at other temperatures, the Q dependences of the EISF have similar shapes. As can be seen from figure 6, the measured EISF is temperature dependent, decreasing with increasing T. This feature is common to all the Laves-phase hydrides studied [12,13,15,24] and Pr 2 Fe 17 H x [9,10]; it can be accounted for in terms of a temperature-dependent fraction of H atoms participating in the localized motion on the time scale of the QENS measurements [12,15]. First, we have to verify whether the observed Q dependence of the EISF in Ce 2 Fe 17 H 5 is consistent with H jump motion over the hexagons formed by the 18g sites.…”

A neutron scattering study of hydrogen dynamics in coarse-grained and nanostructured ZrCr2H3

“…As can be seen from this figure, the temperature dependence of τ −1 l is considerably weaker than that of τ −1 d ; moreover, τ −1 l (T ) deviates from Arrhenius behavior. Both these features are typical of the localized H motion in Laves-phase hydrides [19,34,37]. At room temperature, the jump rate τ −1 l for cg-ZrCr 2 H 3 is a factor of 27 higher than τ −1 d .…”