⁹¹Zr nuclear quadrupole coupling in zircon (ZrSiO₄)

The first measurement of ⁹¹Zr nuclear quadrupole coupling in a solid is reported. The nuclear quadrupole coupling constant (e²qQ/h) and chemical shift anisotropy ( sigma _ax) for ⁹¹Zr, and the chemical shift anisotropy for ²⁹Si, have been determined for zircon (ZrSiO₄) from high-field NMR single-crystal rotation patterns. A striking variation of ⁹¹Zr linewidth with crystal orientation in the field was observed and explained in terms of local variations in the (001) tetragonal axis orientation due to crystal mosaic structure as well as a distribution of local electric-field gradients due to defects.