Markovskiy, N. D. and Muñoz, J. A. and Lucas, M. S. and Li, Chen W. and Delaire, O. and Stone, M. B. and Abernathy, D. L. and Fultz, B. (2011) Nonharmonic phonons in MgB_2 at elevated temperatures. Physical Review B, 83 (17). Art. No. 174301. ISSN 1098-0121 http://resolver.caltech.edu/CaltechAUTHORS:20120530-104815505
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Inelastic neutron scattering was used to measure phonon spectra in MgB_2 and Mg_(0.75)Al_(0.25)B_2 from 7 to 750 K to investigate anharmonicity and adiabatic electron-phonon coupling. First-principles calculations of phonons with a linear response method were performed at multiple unit cell volumes, and the Helmholtz free energy was minimized to obtain the lattice parameters and phonon dynamics at elevated temperature in the quasiharmonic approximation. Most of the temperature dependence of the phonon density of states could be understood with the quasiharmonic approximation, although there was also significant thermal broadening of the phonon spectra. In comparison to Mg_(0.75)Al_(0.25)B_2, in the energy range of 60 to 80 meV the experimental phonon spectra from MgB_2 showed a nonmonotonic change with temperature around 500 K. This may originate from a change with temperature of the adiabatic electron-phonon coupling.
|Additional Information:||© 2011 American Physical Society. Received 21 November 2010; revised manuscript received 11 March 2011; published 4 May 2011. This work was supported by the Department of Energy through the Basic Energy Sciences Grant No. DE-FG02- 03ER46055. The portions of thiswork conducted at Oak Ridge National Laboratory were supported by the Scientific User Facilities Division and by the Division of Materials Sciences and Engineering, Office of Basic Energy Sciences, DOE. This work benefited from DANSE software developed under NSF Grant No. DMR-0520547.|
|Classification Code:||PACS: 74.25.Kc, 78.70.Nx, 71.15.Mb, 74.70.Ad|
|Official Citation:||Nonharmonic phonons in MgB2 at elevated temperatures N. D. Markovskiy, J. A. Muñoz, M. S. Lucas, Chen W. Li, O. Delaire, M. B. Stone, D. L. Abernathy, and B. Fultz Published 4 May 2011 (7 pages) 174301|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Ruth Sustaita|
|Deposited On:||30 May 2012 18:43|
|Last Modified:||26 Dec 2012 15:16|
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