Muñoz, J. A. and Lucas, M. S. and Delaire, O. and Winterrose, M. L. and Mauger, L. and Li, Chen W. and Sheets, A. O. and Stone, M. B. and Abernathy, D. L. and Xiao, Yuming and Chow, Paul and Fultz, B. (2011) Positive Vibrational Entropy of Chemical Ordering in FeV. Physical Review Letters, 107 (11). Art. No. 115501. ISSN 0031-9007 http://resolver.caltech.edu/CaltechAUTHORS:20110928-101310590
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Inelastic neutron scattering and nuclear resonant inelastic x-ray scattering were used to measure phonon spectra of FeV as a B2 ordered compound and as a bcc solid solution. The two data sets were combined to give an accurate phonon density of states, and the phonon partial densities of states for V and Fe atoms. Contrary to the behavior of ordering alloys studied to date, the phonons in the B2 ordered phase are softer than in the solid solution. Ordering increases the vibrational entropy by +0.22±0.03k_B/atom, which stabilizes the ordered phase to higher temperatures. First-principles calculations show that the number of electronic states at the Fermi level increases upon ordering, enhancing the screening between ions, and reducing the interatomic force constants. The effect of screening is larger at the V atomic sites than at the Fe atomic sites.
|Additional Information:||© 2011 American Physical Society. Received 11 December 2010; published 8 September 2011. We thank M. Loguillo for technical support on the ARCS instrument. This work was supported by the Department of Energy through the Basic Energy Sciences Grant DE-FG02-03ER46055. The portions of this work 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. Portions of this work were performed at HPCAT (Sector 16), Advanced Photon Source (APS), Argonne National Laboratory. HPCAT is supported by CIW, CDAC, UNLV and LLNL through funding from DOE-NNSA, DOE-BES and NSF. APS is supported by DOE-BES, under Contract No. DE-AC02-06CH11357. This work benefited from DANSE software developed under NSF Grant No. DMR-0520547.|
|Classification Code:||PACS: 63.20.dd, 63.20.kd, 64.60.Cn, 71.20.Be|
|Official Citation:||Positive Vibrational Entropy of Chemical Ordering in FeV J. A. Muñoz, M. S. Lucas, O. Delaire, M. L. Winterrose, L. Mauger, Chen W. Li, A. O. Sheets, M. B. Stone, D. L. Abernathy, Yuming Xiao, Paul Chow, and B. Fultz Published 8 September 2011|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Ruth Sustaita|
|Deposited On:||29 Sep 2011 16:10|
|Last Modified:||26 Dec 2012 13:43|
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