Manley, M. E. and Fultz, B. and McQueeney, R. J. and Brown, C. M. and Hults, W. L. and Smith, J. L. and Thoma, D. J. and Osborn, R. and Robertson, J. L. (2001) Large harmonic softening of the phonon density of states of uranium. Physical Review Letters, 86 (14). pp. 3076-3079. ISSN 0031-9007 http://resolver.caltech.edu/CaltechAUTHORS:MANprl01
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Phonon density-of-states curves were obtained from inelastic neutron scattering spectra from the three crystalline phases of uranium at temperatures from 50 to 1213 K. The alpha -phase showed an unusually large thermal softening of phonon frequencies. Analysis of the vibrational power spectrum showed that this phonon softening originates with the softening of a harmonic solid, as opposed to vibrations in anharmonic potentials. It follows that thermal excitations of electronic states are more significant thermodynamically than are the classical volume effects. For the alpha-beta and beta-gamma phase transitions, vibrational and electronic entropies were comparable.
|Additional Information:||©2001 The American Physical Society. Received 3 August 2000. M. E. M. acknowledges discussions with A. C. Lawson, D. A. Neumann, D. A. Dimitrov, and B. R. Cooper. The authors also thank A. M. Kelly for help with the sample characterization. This work was supported by the U.S. Department of Energy under Contracts No. DE-FG03-96ER45572 and No. W-31-109-ENG-38.|
|Subject Keywords:||INELASTIC NEUTRON-SCATTERING; VIBRATIONAL ENTROPY; GAMMA-CERIUM|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||16 May 2006|
|Last Modified:||26 Dec 2012 08:52|
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