Biswal, M., Body, M., Legein, C., Corbel, G., Sadoc, A. & Boucher, F. (2012) Structural Investigation of alpha- and beta-Sodium Hexafluoroarsenate, NaAsF6, by Variable Temperature X-ray Powder Diffraction and Multinuclear Solid-State NMR, and DFT Calculations. J. Phys. Chem. C, 116 11682–11693.
Added by: Laurent Cournède (2016-03-10 21:28:39)
|Type de référence: Article
Numéro d'identification (ISBN etc.): 1932-7447
Clé BibTeX: Biswal2012
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Mots-clés: 1st-principles calculations, ab-initio calculations, augmented-wave method, coupling-constants, crystalline polymer electrolytes, density-functional theory, electric-field gradients, na-23 nmr, phase-transitions, structure refinement
Créateurs: Biswal, Body, Boucher, Corbel, Legein, Sadoc
Collection: J. Phys. Chem. C
Consultations : 2/408
Indice de consultation : 2%
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We report the phase transition between the alpha- and beta-phases of NaAsF6 monitored by DTA, variable temperature F-19 solid-state NMR and temperature controlled X-ray powder diffraction (XRPD) as well as their crystalline structures determined from XRPD data. The structural type of beta-NaAsF6 has been determined thanks to F-19 and As-75 solid-state NMR experiments. F-19, Na-73, and As-75 NMR parameters, including F-19-As-75 (1)J coupling, have been measured for both phases. The F-19, Na-73, and As-75 solid-state NMR investigations are in full agreement with both crystalline structures from a qualitative point of view. Chemical shielding tensors have been calculated from the gauge including projector augmented wave approach. The electric field gradient tensors of Na-23 and As-75 have been calculated in alpha-NaAsF6 from the all-electrons method and the projector augmented-wave approach. Two difficulties were encountered: the libration of the rigid and regular AsF6- anions in the beta-phase, highlighted by the atomic anisotropic displacement parameters for F, which leads to erroneous shortened As-F bond length, and the overestimation of the As-F bond length with the PBE functional used in the density functional theory calculations. We show that both difficulties can be overcome by full optimization and rescaling of the cell parameters of the crystalline structures. Additionally, a linear correlation is observed between experimental Na-23 delta(iso) values and calculated Na-23 sigma(iso) values from previously reported data and from our own measurements and calculations.
Added by: Laurent Cournède