Abstract
Information on both radial and angular atomic coordinations is provided by the quadrupole interaction between the quadrupole moment of the atomic nuclei and the electric field gradients (EFGs) originating from the distribution of electric charges around the nuclei. 69Ga and 71Ga are quadrupolar nuclei active in NMR. Their spectra are recorded in amorphous GaF3 which may be considered as a model compound for disordered fluorides with fluorine corner sharing octahedra. An unique and continuous quadrupolar parameter Czjzek distribution allows us to simulate the experimental spectra. The measured chemical shifts indicate that the Ga3+ ions are at the centre of (GaF6)3- octahedra in the amorphous GaF3 phase.A polarizable point charge model is used to explain NMR quadrupolar parameters which are related to the electric field gradients at the Ga site. Lattice summations are performed in the direct space over spherical volumes. Atomic position sets generated by molecular dynamics are shown to give quadrupolar parameter distributions which look like Czjzek ones whatever the EFG calculation approximations. Provided the polarizabilities are adjusted, they allow us to reconstruct the experimental NMR spectra which correspond in any case to slightly distorted (GaF6)3- octahedra. The present approach may be applied to any ionic disordered compound which contains quadrupolar nuclei and used to quantify short range order around such nuclei.