Ultrasonic Velocity and Attenuation in Alkali Halides Containing CN⁻ I. Experimental Results

Abstract

Abstract The ultrasonic velocity and attenuation were measured in KCl, KBr, KI, and NaCl containing CN − as a function of acoustic mode, temperature, concentration, frequency, plastic deformation, and static bias stress. The results are not compatible with stress ordering of an elastic dipole tensor represented by an ellipsoid of rotation with CN − axes having 〈100〉 equilibrium positions, as had been inferred from other measurements. A thermally activated relaxation peak was observed for a CN − dimer with a barrier height of 0.008 eV. In NaCl the CN − reorients by thermal activation over a 0.035 eV barrier as opposed to the tunneling in the potassium halides.