Effect of Pressure on the Elastic Parameters and Structure of CdS

The effective elastic constants of CdS have been measured by the ultrasonic pulse-echo method as a function of hydrostatic pressure to 4 kbar. The logarithmic pressure derivatives determined were $\frac{d\ln C_{11}}{\mathrm{dP}}=3.56\mathrm{}$, $\frac{d\ln C_{33}}{\mathrm{dP}}=3.44\mathrm{}$, $\frac{d\ln C_{13}}{\mathrm{dP}}=10.0\mathrm{}$, $\frac{d\ln C_{44}}{\mathrm{dP}}=-4.22\mathrm{}$, $\frac{d\ln C_{66}}{\mathrm{dP}}=-4.97\mathrm{}$ (in ${\mathrm{Mbar}}^{-1\mathrm{}}$). A continuous-deformation model of the wurtzite-to-rocksalt pressure-induced transformation in CdS is presented. A combination of elastic constants characteristic of this deformation is derived and the transformation discussed in terms of a microscopic shear mechanism based on these results.