Third Harmonic of an Initially Sinusoidal Ultrasonic Wave in Copper

The amplitude of the third harmonic of an initially sinusoidal ultrasonic wave is measured in the [100] direction in copper, both directly and by a pulse overlap technique. The value of the third-order elastic constant C111=−16 × 1012 dyn/cm2 is obtained from measurements of third harmonic amplitudes of the order of 10−3 Å. The contribution of the fourth-order constant C1111 to these amplitudes appears to be negligible.