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Temperature dependence of phonons in FeGe_2

Smith, Hillary L. and Shen, Yang and Kim, Dennis S. and Yang, Fred C. and Adams, C. P. and Li, Chen W. and Abernathy, D. L. and Stone, M. B. and Fultz, B. (2018) Temperature dependence of phonons in FeGe_2. Physical Review Materials, 2 (10). Art. No. 103602. ISSN 2475-9953.

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Inelastic neutron scattering was used to measure phonon dispersions in a single crystal of FeGe_2 with the C16 structure at 300, 500, and 635 K. Phonon densities of states (DOS) were also measured on polycrystalline FeGe_2 from 325 to 1050 K, and the Fe partial DOS was obtained from polycrystalline ^(57)FeGe_2 at 300 K using nuclear resonant inelastic x-ray scattering. The dominant feature in the temperature dependence of the phonon spectrum is thermal broadening of high-energy modes. The energy shifts of the low- and high-energy parts of the spectrum were almost the same. DFT calculations performed with the quasiharmonic approximation gave results in moderate agreement with the experimental thermal energy shifts, although the isobaric Grüneisen parameter calculated from the quasiharmonic model was smaller than that from measurements. The thermal broadening of the phonon spectrum and dispersions, especially at high energies, indicates a cubic anharmonicity to second order that should also induce phonon shifts. We show that different anharmonic contributions cancel out, giving average phonon shifts in moderate agreement to calculations with the quasiharmonic approximation. The different parts of the large phonon contribution to the entropy are separated for FeGe_2, showing modest but interpretable anharmonic contributions.

Item Type:Article
Related URLs:
URLURL TypeDescription
Kim, Dennis S.0000-0002-5707-2609
Yang, Fred C. 0000-0002-5615-5170
Li, Chen W.0000-0002-0758-5334
Abernathy, D. L.0000-0002-3533-003X
Stone, M. B.0000-0001-7884-9715
Fultz, B.0000-0002-6364-8782
Alternate Title:Temperature dependence of phonons in FeGe2
Additional Information:© 2018 American Physical Society. Received 25 November 2017; revised manuscript received 5 August 2018; published 9 October 2018. This work was supported by DOE BES under Contract No. DE-FG02-03ER46055. A portion of this research at Oak Ridge National Laboratory's Spallation Neutron Source was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. Portions of this work were performed at HPCAT (Sector 16), Advanced Photon Source (APS), Argonne National Laboratory. HPCAT operations are supported by DOE-NNSA under Award No. DE-NA0001974 and DOE-BES under Award No. DE-FG02-99ER45775, with partial instrumentation funding by NSF. The Advanced Photon Source is a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. This work benefited from danse software developed under NSF Grant No. DMR-0520547. Part of the calculations performed herein were made possible by resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
Funding AgencyGrant Number
Department of Energy (DOE)DE-FG02-03ER46055
Department of Energy (DOE)DE-NA0001974
Department of Energy (DOE)DE-FG02-99ER45775
Department of Energy (DOE)DE-AC02-06CH11357
Department of Energy (DOE)DE-AC02-05CH11231
Issue or Number:10
Record Number:CaltechAUTHORS:20181009-094209133
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:90185
Deposited By: Tony Diaz
Deposited On:09 Oct 2018 16:54
Last Modified:16 Mar 2020 18:44

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