The Adiabatic Elastic Constants of Rock Salt

The velocities of propagation of 10-Mc/sec longitudinal and transverse sound waves in single crystals of rock salt have been measured over the temperature range from 60°K to 300°K by means of the ultrasonic pulse method. From these velocities the adiabatic elastic constants have been calculated, with the results that $c_{11}=4.828\mathrm{}\pm 0.015$, $c_{44}=1.273\mathrm{}\pm 0.005$, and $c_{12}=1.276\mathrm{}\pm 0.025$ at 300°K in units of dyne/${\mathrm{cm}}^2$×${10}^{11}$. The values of these elastic constants extrapolated to absolute zero temperature are in these units, 5.750, 1.327, and 0.986, respectively. The adiabatic compressibility has been calculated from $c_{11}$ and $c_{12}$ and is 4.07×${10}^{-12\mathrm{}}$ ${\mathrm{cm}}^2$/dyne at 300°K. The Debye characteristic temperature is computed to be 292.6±0.5°K at $T=0\mathrm{}$°K.