Ultrasonic studies of benzophenone single crystals I. Influence of defect structure

Abstract

Ultrasonic velocities have been measured using oriented single-crystal slices of benzophenone containing various degrees of imperfection arising either from the method of crystal growth or as a result of subsequent mechanical deformation. It was found that, provided that the dislocation density was below 10⁴cm⁻², then intrinsic velocities could be measured to an accuracy of 0.04%. The imprecision of the measurements increased to a value of 0.6% at a dislocation density of 10⁷ cm⁻². These results define the quality of organic single crystals which must be used for intrinsic elastic constant measurements.