Quadrupole interaction at111Cd nuclein in single-crystalline thallium

The quadrupole interaction of¹¹¹Cd nuclei in a single crystal of hexagonal thallium has been investigated for different geometries and sample temperatures employing the perturbed - angular correlation technique. The observed variation of the electric field gradient with temperature is attributed to local modes of thermal vibrations of the Cd impurities. An analytical relationship has been derived from lattice-dynamical models, expressing the temperature dependence in terms of impurity-host mass ratios and local force-constants.