Third-Order Elastic Coefficients of Quartz

All 14 third‐order elastic coefficients of quartz have been calculated from the measured transit times for small‐amplitude ultrasonic waves as functions of applied stress. Thirty‐four different experimental runs were made, ten under hydrostatic pressure, and 24 under uniaxial stress. The data permit calculation of the 14 coefficients with 20 crosschecks. Our recommended values at 25°C, based on a least‐squares fit, are as follows, all in 10¹² dyn/cm². $$\begin{array}{ccc}\mathrm{Coefficient}& \mathrm{Value}& \mathrm{Standard\; error}\\ & & \\ C_{111}& \text{−2.10}& \text{0.07}\\ C_{112}& \text{−3.45}& \text{0.06}\\ C_{113}& \text{+0.12}& \text{0.06}\\ C_{114}& \text{−1.63}& \text{0.05}\\ C_{123}& \text{−2.94}& \text{0.05}\\ C_{124}& \text{−0.15}& \text{0.04}\\ C_{133}& \text{−3.12}& \text{0.07}\\ C_{134}& \text{+0.02}& \text{0.04}\\ C_{144}& \text{−1.34}& \text{0.07}\\ C_{155}& \text{−2.00}& \text{0.08}\\ C_{222}& \text{−3.32}& \text{0.08}\\ C_{333}& \text{−8.15}& \text{0.18}\\ C_{344}& \text{−1.10}& \text{0.07}\\ C_{444}& \text{−2.76}& \text{\hspace{0.17em}0.17.}\end{array}$$