Quasielastic neutron scattering study of hydrogen motion in C15-type ?
Abstract
In order to clarify the mechanism of hydrogen diffusion in cubic Laves phase 0953-8984/10/8/012/img7, we have performed high-resolution quasielastic neutron scattering measurements on 0953-8984/10/8/012/img8 (x = 0.6 and 1.1) in the temperature range 10-320 K. It is found that the diffusive motion of hydrogen in this system can be described in terms of two jump processes: the fast localized H motion within hexagons formed by interstitial g 0953-8984/10/8/012/img9 sites and the slower hopping from one hexagon to the other. This model is also supported by neutron diffraction measurements showing that the sublattice of g sites in 0953-8984/10/8/012/img10 is split into hexagons well separated from each other. The behaviour of the elastic incoherent structure factor for 0953-8984/10/8/012/img8 suggests that only a fraction of the H atoms participate in the fast localized motion, and this fraction increases with temperature. Comparison of the properties of 0953-8984/10/8/012/img8 and other Laves phase hydrides with g-site occupation shows a clear correlation between the parameters of the two jump processes and the g-g distances 0953-8984/10/8/012/img13 (within the hexagons) and 0953-8984/10/8/012/img14 (between different hexagons).
- Publication:
-
Journal of Physics Condensed Matter
- Pub Date:
- March 1998
- DOI:
- 10.1088/0953-8984/10/8/012
- Bibcode:
- 1998JPCM...10.1787S