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dc.contributor.authorFoury-Leylekian, P.-
dc.contributor.authorPetit, S.-
dc.contributor.authorMirebeau, I.-
dc.contributor.authorAndré, G.-
dc.contributor.authorDe Souza, M.-
dc.contributor.authorLang, M.-
dc.contributor.authorRessouche, E.-
dc.contributor.authorMoradpour, A.-
dc.contributor.authorPouget, J. P.-
dc.identifier.citationPhysical Review B - Condensed Matter and Materials Physics, v. 88, n. 2, 2013.-
dc.description.abstractWe present a detailed low-temperature investigation of the statics and dynamics of the anions and methyl groups in the organic conductors (TMTSF) 2PF6 and (TMTSF)2AsF6 (TMTSF: tetramethyl-tetraselenafulvalene). The 4 K neutron-scattering structure refinement of the fully deuterated (TMTSF)2PF6-D12 salt allows locating precisely the methyl groups at 4 K. This structure is compared to the one of the fully hydrogenated (TMTSF)2PF6-H12 salt previously determined at the same temperature. Surprisingly, it is found that deuteration corresponds to the application of a negative pressure of 5×102 MPa to the H12 salt. Accurate measurements of the Bragg intensity show anomalous thermal variations at low temperature both in the deuterated PF 6 and AsF6 salts. Two different thermal behaviors have been distinguished. Small Bragg-angle measurements reflect the presence of low-frequency modes at characteristic energies θE = 8.3 K and θE = 6.7 K for the PF6-D12 and AsF6-D12 salts, respectively. These modes correspond to the low-temperature methyl group motion. Large Bragg-angle measurements evidence an unexpected structural change around 55 K, which probably corresponds to the linkage of the anions to the methyl groups via the formation of F...D-CD2 bonds observed in the 4 K structural refinement. Finally we show that the thermal expansion coefficient of (TMTSF)2PF6 is dominated by the librational motion of the PF6 units. We quantitatively analyze the low-temperature variation of the lattice expansion via the contribution of Einstein oscillators, which allows us to determine for the first time the characteristic frequency of the PF6 librations: θE ≈ 50 K and θE = 76 K for the PF6-D12 and PF6-H12 salts, respectively. © 2013 American Physical Society.en
dc.titleLow-temperature structural effects in the (TMTSF)2PF6 and AsF6 Bechgaard saltsen
dc.contributor.institutionCNRS UMR 8502-
dc.contributor.institutionCEA-CNRS UMR 12-
dc.contributor.institutionUniversidade Estadual Paulista (UNESP)-
dc.contributor.institutionSFB/TR 49-
dc.description.affiliationLaboratoire de Physique des Solides Université Paris-Sud CNRS UMR 8502, F-91405 Orsay Cedex-
dc.description.affiliationLaboratoire Léon Brillouin CEA-CNRS UMR 12, F-91191 Gif-sur-Yvette cedex-
dc.description.affiliationInstituto de Geociências e Ciências Exatas-IGCe Unesp-Univ Estadual Paulista Departamento de Física, Cx. Postal 178, 13506-900 Rio Claro (SP)-
dc.description.affiliationPhysikalisches Institut Goethe-Universität Frankfurt SFB/TR 49, D-60438 Frankfurt (M)-
dc.description.affiliationSPSMS UMR-E CEA/UJF-Grenoble 1 INAC, Grenoble, F-38054-
dc.description.affiliationUnespInstituto de Geociências e Ciências Exatas-IGCe Unesp-Univ Estadual Paulista Departamento de Física, Cx. Postal 178, 13506-900 Rio Claro (SP)-
dc.rights.accessRightsAcesso restrito-
dc.relation.ispartofPhysical Review B: Condensed Matter and Materials Physics-
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