Temperature dependence of alkali-metal rattling dynamics in the β-pyrochlores, AOs2O6 (A = K, Rb, Cs), from MD simulation

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dc.contributor.authorShoko, Een_AU
dc.contributor.authorPeterson, VKen_AU
dc.contributor.authorKearley, GJen_AU
dc.date.accessioned2016-10-26T04:35:01Zen_AU
dc.date.available2016-10-26T04:35:01Zen_AU
dc.date.issued2014-05-16en_AU
dc.date.statistics2016-10-26en_AU
dc.description.abstractWe investigate the temperature response of the alkali-metal rattling modes in β-pyrochlores, AOs2O6 (A = K, Rb, Cs), from the results of ab initio molecular dynamics (MD) simulations performed at 20 K, 100 K and 300 K. Our results show that the temperature response of the T1u mode is clearly different from that of the T2g mode for all three pyrochlores. In this regard, two features are of particular note for both K and Rb; (1) the T1u mode exhibits a distinctly stronger softening response with decreasing temperature compared to the T2g mode, and (2) the T1u mode becomes stronger and sharper with decreasing temperature. These two findings suggest that the T1u mode is significantly more anharmonic and sensitive to the cage dynamics than the T2g mode. Examination of the local potentials around the alkali-metal atoms reveals that K has the flattest and most anharmonic potential at all temperatures while Cs exhibits the narrowest potential. The temperature dependence of the local potentials reveals that, for K, the potential at a higher temperature is not a simple extrapolation to higher energy of that at a lower temperature. Instead, we find significant reconstruction of the potential at different temperatures. Finally, we explore the temperature response of the coupling between the alkali metals and find a complex temperature dependence which suggests that the origin of the coupling may be more complex than a pure Coulomb interaction. We also find an unexpected increase in the static disorder of the system at low temperatures for the K and Rb pyrochlores. © 2014 IOP Publishing Ltden_AU
dc.identifier.articlenumber235401en_AU
dc.identifier.citationShoko, E., Peterson, V. K. & Kearley, G. J. (2014). Temperature dependence of alkali-metal rattling dynamics in the β-pyrochlores, AOs2O6 (A = K, Rb, Cs), from MD simulation. Journal of Physics: Condensed Matter, 26(23), 235401. doi:10.1088/0953-8984/26/23/235401en_AU
dc.identifier.govdoc7443en_AU
dc.identifier.issn1361-648Xen_AU
dc.identifier.issue23en_AU
dc.identifier.journaltitleJournal of Physics: Condensed Matteren_AU
dc.identifier.uri https://iopscience.iop.org/article/10.1088/0953-8984/26/23/235401/metaen_AU
dc.identifier.urihttp://apo.ansto.gov.au/dspace/handle/10238/7907en_AU
dc.identifier.volume26en_AU
dc.language.isoenen_AU
dc.publisherIOP Scienceen_AU
dc.subjectPyrochloreen_AU
dc.subjectAlkali metalsen_AU
dc.subjectMoleculesen_AU
dc.subjectThermoelectricityen_AU
dc.subjectTemperature rangeen_AU
dc.subjectAcid neutralizing capacityen_AU
dc.titleTemperature dependence of alkali-metal rattling dynamics in the β-pyrochlores, AOs2O6 (A = K, Rb, Cs), from MD simulationen_AU
dc.typeJournal Articleen_AU
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