Acoustic Velocities and Phase Transitions in Molybdenum under Strong Shock Compression

We present acoustic velocity data that demonstrate a high-pressure solid-solid phase transition in molybdenum at about 2. 1 Mbar and 4100 K. This observation is supported here by first-principles theoretical calculations which predict a zero-temperature bcc hcp transition within our experimental pressure range. In addition, our results show the melting transition for shock-compressed Mo at about 3. 9 Mbar and 10000 K.