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EnglishExtended x-ray-absorption fine-structure (EXAFS) of copper has been measured from 4 to 500 K and analyzed by the cumulant method, to check the effectiveness of EXAFS as a probe of local dynamics and thermal expansion. The comparison between parallel mean square relative displacements (MSRD) of the first four coordination shells has allowed detecting a significant deviation from a pure Debye behavior. The first- shell EXAFS thermal expansion is larger than the crystallographic one: the difference has allowed evaluating the perpendicular MSRD, whose Debye temperature is slightly larger than the one of the parallel MSRD, due to anisotropy effects. High-order first-shell cumulants are in good agreement with quantum perturbative mod- els. The anharmonic contribution to the first-shell parallel MSRD amounts to less than 1.5 percent. The third cumulant cannot be neglected in the analysis, if accurate values of the first cumulant are sought; it cannot however be used to directly estimate the thermal expansion. The shape of the effective pair potential is independent of temperature; a rigid shift, partially due to the relative motion perpendicular to the bond direction, is however observed.
| Titolo: | Extended x-ray-absorption fine-structure measurements of copper: local dynamics, anharmonicity, and thermal expansion | |
| Autori: | Fornasini, Paolo; S. A., Beccara; Dalba, Giuseppe; Grisenti, Rolly; Sanson, Andrea; M., Vaccari; F., Rocca | |
| Autori Unitn: | ||
| Titolo del periodico: | PHYSICAL REVIEW. B, CONDENSED MATTER AND MATERIALS PHYSICS | |
| Anno di pubblicazione: | 2004 | |
| Numero e parte del fascicolo: | 17 | |
| Codice identificativo Scopus: | 2-s2.0-12244288353 | |
| Codice identificativo ISI: | WOS:000225477000056 | |
| Digital Object Identifier (DOI): | http://dx.doi.org/10.1103/PhysRevB.70.174301 | |
| Handle: | http://hdl.handle.net/11572/6872 | |
| Appare nelle tipologie: | 03.1 Articolo su rivista (Journal article) |
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