ANSTO Publications Online >
Journal Publications >
Journal Articles >

Please use this identifier to cite or link to this item: http://apo.ansto.gov.au/dspace/handle/10238/7906

Title: Novel rattling of K atoms in aluminium-doped defect pyrochlore tungstate
Authors: Shoko, E
Kearley, GJ
Peterson, VK
Mutka, H
Koza, MM
Yamaura, J
Hiroi, Z
Thorogood, GJ
Keywords: PYROCHLORE
ALUMINIUM
SUPERCONDUCTIVITY
ATOMS
PHONONS
THERMOELECTRIC MATERIALS
Issue Date: 4-Jul-2014
Publisher: IOP Science
Citation: Shoko, E., Kearley, G. J., Peterson, V. K., Mutka, H., Koza, M. M., Yamaura, J., ., . . . Thorogood, G. J. (2014). Novel rattling of K atoms in aluminium-doped defect pyrochlore tungstate. Journal of Physics: Condensed Matter, 26(30), 5401-5401. doi: http://dx.doi.org/10.1088/0953-8984/26/30/305401
Abstract: Rattling dynamics have been identified as fundamental to superconductivity in defect pyrochlore osmates and aluminium vanadium intermetallics, as well as low thermal conductivity in clathrates and filled skutterudites. Combining inelastic neutron scattering (INS) measurements and ab initio molecular dynamics (MD) simulations, we use a new approach to investigate rattling in the Al-doped defect pyrochlore tungstates: AAl0.33W1.67O6 (A = K, Rb, Cs). We find that although all the alkali metals rattle, the rattling of the K atoms is unique, not only among the tungstates but also among the analogous defect osmates, KOs2O6 and RbOs2O6. Detailed analysis of the MD trajectories reveals that two unique features set the K dynamics apart from the rest, namely, (1) quasi one-dimensional local diffusion within a cage, and (2) vibration at a range of frequencies. The local diffusion is driven by strongly anharmonic local potentials around the K atoms exhibiting a double-well structure in the direction of maximum displacement, which is also the direction of local diffusion. On the other hand, vibration at a range of frequencies is a consequence of the strong anisotropy in the local potentials around the K atoms as revealed by directional magnitude spectra. We present evidence to show that it is the smaller size rather than the smaller mass of the K rattler which leads to the unusual dynamics. Finally, we suggest that the occurrence of local diffusion and vibration at a range of frequencies in the dynamics of a single rattler, as found here for the K atoms, may open new possibilities for phonon engineering in thermoelectric materials. © 2014, IOP Publishing Ltd.
URI: http://dx.doi.org/10.1088/0953-8984/26/30/305401
http://apo.ansto.gov.au/dspace/handle/10238/7906
Appears in Collections:Journal Articles

Files in This Item:

There are no files associated with this item.

Items in APO are protected by copyright, with all rights reserved, unless otherwise indicated.

 

Valid XHTML 1.0! DSpace Software Copyright © 2002-2010  Duraspace - Feedback