Nuclear Quadrupole Interactions in Beryllium Oxide

Abstract

The importance of the contribution from higher multipole moments of oxygen ions to the electric field gradient at nuclei in a wurtzite-type ionic oxide, namely, beryllium oxide, is considered and, in particular, oxygen dipole moments are found to contribute significantly to the field gradient at beryllium ion sites. The dipolar polarizability of an oxygen ion bound in a beryllium oxide lattice is analyzed and a value of 2.19 \AA{}${\mathrm{A}}^{3}$ is obtained. Using 7.0 \AA{}${\mathrm{A}}^{5}$ for the quadrupolar polarizability of the same ion and considering the slight uncertainty associated with the sublattice displacement parameter $u$, the experimental quadrupole coupling constant for the ${\mathrm{Be}}^{9}$ nuclei, \ifmmode\pm\else\textpm\fi{}41\ifmmode\pm\else\textpm\fi{}4 kc/sec, can be explained. The quadrupole coupling constant for ${\mathrm{O}}^{17}$ nuclei is also investigated and presented as a function of $u$. In this case, oxygen dipole moments do not contribute because of lattice symmetry; oxygen quadrupole moments do contribute, however.