Atom clusters and vibrational excitations in chemically-disordered Pt{sub 3}{sup 57}Fe
- Division of Engineering and Applied Science, California Institute of Technology, Pasadena, California 91125 (United States)
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States)
Inelastic nuclear resonant scattering spectra of {sup 57}Fe atoms were measured on crystalline alloys of Pt{sub 3}{sup 57}Fe that were chemically disordered, partially ordered, and L1{sub 2} ordered. Phonon partial density of states curves for {sup 57}Fe were obtained from these spectra. Upon disordering, about 10% of the spectral intensity underwent a distinct shift from 25 to 19 meV. This change in optical modes accounted for most of the change of the vibrational entropy of disordering contributed by Fe atoms, which was (+0.10 {+-} 0.03) k{sub B} (Fe atom){sup -1}. Prospects for parametrizing the vibrational entropy with low-order cluster variables were assessed. To calculate the difference in vibrational entropy of the disordered and ordered alloys, the clusters must be large enough to account for the abundances of several of the atom configurations of the first-nearest-neighbor shell about the {sup 57}Fe atoms. (c) 2000 The American Physical Society.
- OSTI ID:
- 20216575
- Journal Information:
- Physical Review. B, Condensed Matter and Materials Physics, Vol. 61, Issue 21; Other Information: PBD: 1 Jun 2000; ISSN 1098-0121
- Country of Publication:
- United States
- Language:
- English
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