Calculation of Electric-Field-Gradient Tensor for a Single Crystal of Paramagnetic CuCl2·2H2O

Abstract

The electric-field-gradient tensor at the chlorine site in Cu${\mathrm{Cl}}_2$·2${\mathrm{H}}_2$O is calculated assuming ionic point-charge distribution at the lattice sites and taking into account the effect of the charges and effective (permanent+induced) dipole moments within a sphere of 40 Å around the site of interest. The theoretical quadrupole resonance frequency for the ${\mathrm{Cl}}^{-}$ ion, $I=\frac{3}{2}$, assuming the antishielding factor to be -27.04, comes out to be 8.67 Mc/sec, which is quite close to the experimental value of 9.05 Mc/sec. The orientation of the principal axes of the tensor with respect to the crystalline $a$, $b$, $c$ axes and the asymmetry parameter $\eta$ are also calculated.