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  Vibrational dynamics of the type-I clathrates A8Sn442 (A = Cs, Rb, K) from lattice-dynamics calculations, inelastic neutron scattering, and specific heat measurements

Candolfi, C., Koza, M., Aydemir, U., Carrillo-Cabrera, W., Grin, Y., Steglich, F., et al. (2020). Vibrational dynamics of the type-I clathrates A8Sn442 (A = Cs, Rb, K) from lattice-dynamics calculations, inelastic neutron scattering, and specific heat measurements. Journal of Applied Physics, 127: 145104, pp. 1-15. doi:10.1063/1.5117217.

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Item Permalink: http://hdl.handle.net/21.11116/0000-0006-4E6E-9 Version Permalink: http://hdl.handle.net/21.11116/0000-0006-4E70-5
Genre: Journal Article

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 Creators:
Candolfi, C.1, Author              
Koza, M.M.2, Author
Aydemir, U.2, Author
Carrillo-Cabrera, W.3, Author              
Grin, Yu.4, Author              
Steglich, F.5, Author              
Baitinger, M.6, Author              
Affiliations:
1Max Planck Institute for Chemical Physics of Solids, Max Planck Society, ou_1863404              
2External Organizations, ou_persistent22              
3Chemical Metal Science, Max Planck Institute for Chemical Physics of Solids, Max Planck Society, ou_1863405              
4Juri Grin, Chemical Metal Science, Max Planck Institute for Chemical Physics of Solids, Max Planck Society, ou_1863413              
5Frank Steglich, Physics of Quantum Materials, Max Planck Institute for Chemical Physics of Solids, Max Planck Society, ou_1863467              
6Michael Baitinger, Chemical Metal Science, Max Planck Institute for Chemical Physics of Solids, Max Planck Society, ou_1863416              

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Free keywords: Atoms, Calculations, Cesium, Cesium compounds, Dynamics, Hydrates, Inelastic neutron scattering, Lattice vibrations, Phonons, Rubidium compounds, Temperature distribution, Thermal variables measurement, Thermoacoustics, Clathrate structure, Dynamics calculations, Low energy regions, Low-energy spectra, Low-temperature specific heat, Temperature dependence, Vibrational density of state, Vibrational dynamics, Specific heat
 Abstract: We report on a joint theoretical and experimental study of the vibrational dynamics of the type-I clathrates A8Sn44□2 (A = K, Rb, Cs, and □ stands for a vacancy) by high-resolution inelastic neutron scattering experiments combined with low-temperature specific heat measurements (2-300 K). Ab initio lattice dynamics calculations were performed on hypothetical vacancy-free A8Sn46 clathrates in order to determine the phonon dispersions and vibrational density of states Z (ω). The temperature dependence of the generalized vibrational density of states (GVDOS) was traced from 420 K down to 50 K, paying particular attention to the low-energy region of the GVDOS spectra. In the Cs and Rb compounds, the inelastic signal at low energies is dominated by several peaks mainly associated with the dynamics of the alkali metal atoms A in the polyhedral cages of the clathrate structure. In contrast, the low-energy spectrum of the K compound features a more pronounced contribution of the weighed modes of the framework Sn atoms. Upon cooling, the A-weighted modes soften regardless of the nature of the alkali element. The shift observed is similar for the three compounds and of small amplitude, suggestive of a dominant quasi-harmonic behavior above 50 K. The distinct dynamics of the K atoms in comparison to Cs and Rb is further demonstrated by the analyses of the low-temperature specific heat data, indicating that the low-energy Sn-weighted modes cannot be described by a Debye model with Einstein-like contributions. © 2020 Author(s).

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Language(s): eng - English
 Dates: 2020-04-142020-04-14
 Publication Status: Published in print
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: -
 Identifiers: DOI: 10.1063/1.5117217
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Title: Journal of Applied Physics
  Abbreviation : J. Appl. Phys.
Source Genre: Journal
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Publ. Info: New York, NY : AIP Publishing
Pages: - Volume / Issue: 127 Sequence Number: 145104 Start / End Page: 1 - 15 Identifier: ISSN: 0021-8979
CoNE: https://pure.mpg.de/cone/journals/resource/991042723401880