Multinuclear NMR and DFT calculations on the LiFePO<sub>4</sub>.OH and FePO<sub>4</sub>.H<sub>2</sub>O homeotypic phases
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en
Article de revue
Ce document a été publié dans
Journal of Physical Chemistry C. 2011, vol. 115, n° 32, p. 16234-16241
American Chemical Society
Résumé en anglais
<sup>7</sup>Li, <sup>31</sup>P, and <sup>1</sup>H MAS NMR spectra and magnetic properties are reported for LiFePO<sub>4</sub>*OH and FePO<sub>4</sub>*H<sub>2</sub>O. The former shows no Curie-Weiss-type behavior up to room ...Lire la suite >
<sup>7</sup>Li, <sup>31</sup>P, and <sup>1</sup>H MAS NMR spectra and magnetic properties are reported for LiFePO<sub>4</sub>*OH and FePO<sub>4</sub>*H<sub>2</sub>O. The former shows no Curie-Weiss-type behavior up to room temperature, while the latter tends to such a behavior in a restricted temperature range. Calculation strategies are discussed for the NMR shifts that result from Fermi contact interaction with the high spin Fe<sup>3+</sup> ions. Zero Kelvin electron spin densities obtained by averaging over the ion size using VASP (with PAW potentials) range with those obtained at the nucleus from WIEN2k, with the GGA and GGA+U methods. The latter values have been scaled with the temperature of the NMR measurement by using the experimental magnetic susceptibility, yielding calculated NMR shifts. The agreement is quite satisfactory, but very much dependent on the exchange correlation potential used for the calculation. Possible reasons for this are discussed, also considering the difference in magnetic behaviors.< Réduire
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