VSE knjižnice (vzajemna bibliografsko-kataložna baza podatkov COBIB.SI)
  • Li_2FeSiO_4 polymorphs probed by 6^Li MAS NMR and 57^Fe Mössbauer spectroscopy [Gregor Mali ... [et al.]]
    Mali, Gregor, 1971- ...
    Several 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.
    Vir: Chemistry of materials. - ISSN 0897-4756 (Vol. 23, no. 11, 2011, str. 2735-2744)
    Vrsta gradiva - članek, sestavni del
    Leto - 2011
    Jezik - angleški
    COBISS.SI-ID - 4676890

vir: Chemistry of materials. - ISSN 0897-4756 (Vol. 23, no. 11, 2011, str. 2735-2744)