Temperature Dependence of the Adiabatic Elastic Moduli of Single-Crystal Alpha Uranium

The ultrasonic-wave velocities in small alpha-uranium single crystals have been measured at various temperatures using the phase-comparison technique. Details in the experimental procedure, direct computation of the stiffness moduli, and cross-checking by indirect methods are given. The temperature dependence of the moduli are reported for the range −195° to +300°C for c11, c22, and c33 and −195° to +35°C for the remaining 6 principal moduli. The results show a very marked abnormal temperature dependence of the elasticity in the [100] direction; c11 decreases with temperature below −17.2°C and the linear compressibility in [100] increases from +35° to −195°C. The bulk modulus passes through a maximum at −100°C. These abnormalities indicate a strong temperature dependence of the electron interactions involved in the second nearest-neighbor bond.