Sound Velocities at High Pressures and Shock-Melting of Copper

Sound velocities of copper at high shock pressures were determined by using optical analyzer technique under on-dimensional strain condition. The measured pressure range was from 125 GPa to 170 GPa. Combined with the data given earlier by Broberg, Morris et al., Altshuler et al., and ours, a comprehensive analysis for sound velocities at pressures of 0~170 GPa was also made. It shows the elastic sound velocity cl of solid-state copper, when the pressure is between 0~156 GPa, monotonically increases with the increasing of shock pressure and can be represented by the following equation ln cl=1.565 888-2.645 48810-2ln p+2.710 68110-2ln2p. Relations errors between the data deduced from the above equation and the measurement are less than 1.3%. Moreover, the shock-melting, marked as the sudden drop of sound velocity in c-p relation, occurs at 156~159 GPa and completes at about 170 GPa, for which a rather satisfactory verification is also acquired by the Lindeman melting-law in the analysis.