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AvtorMali, Gregor, 1971-
Sirisopanaporn, Chutchamon
Masquelier, Christian
Hanžel, Darko
Dominko, Robert
Naslov Li [sub] 2 FeSiO [sub] 4 polymorphs probed by 6 [sup] Li MAS NMR and 57 [sup] Fe Mössbauer spectroscopy / Gregor Mali ... [et al.]
Vrsta/vsebinatype of material članek - sestavni del
Fizični opisstr. 2735-2744
OpombeSodelavci: Chutchamon Sirisopanaporn, Christian Masquelier, Darko Hanzel, Robert Dominko
Bibliografija: str. 2743-2744
Predmetne oznake (nekontrolirane)strukturna kemija / spektroskopija / baterije
PovzetekSeveral samples of pure Li2FeSiO4 polymorphs, prepared by hydrothermal synthesis and then quenched from either 400 °C (Pmn21), 700 °C (P21/n), or 900°C (Pmnb), were thoroughly investigated by Mssbauer and NMR spectroscopy. 57Fe Mssbauer spectroscopy showed that (i) iron in all the polymorphs existed in the divalent oxidation state, and (ii) chemical shifts and quadrupolar splittings correlated well with Fe-O bond lengths. 6Li MAS NMR spectra of the three different polymorphs exhibit substantially different spinning-sideband patterns and slightly different isotropic shifts. The sideband patterns stemming from the anisotropic electron-nucleus dipole-dipole interaction reflect the arrangement of paramagnetic iron ions around lithium nuclei and allowed unambiguous assignments of 6Li MAS NMR signals to crystallographicallynonequivalent Li sites. Analysis of isotropic NMR shifts of 6Li nuclei revealed that they comprised two contributions of comparable magnitude, a hyperfine (contact) shift and a pseudo-contact shift. Based on the structural models of Li2FeSiO4, both contributions could be successfully predicted by first-principles calculations. The contact shift was obtained from the hyperfine-coupling constant on 6Li nuclei, which was calculated within a DFT/PAW approach, and the pseudo-contact shift was derived from the electron-nucleus dipolar matrix and the g-tensor, which was computed within the DFT/GIPAW frame.
Glej publikacijo TI=Chemistry of materials ISSN: 0897-4756.- Vol. 23, no. 11 (2011), str. 2735-2744

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