Anomalous elastic–plastic transition of MgO under shock compression

The particle velocity profiles of an MgO single crystal under shock compression were measured up to a pressure of 35 GPa by a velocity interferometer system for any reflector using a LiF window combined with a powder gun. The Hugoniot-elastic limit (HEL) of MgO along the ⟨100⟩ direction was 2.9–4.3 GPa and the initial elastic waves contain some oscillations. Along the ⟨110⟩ direction, the HEL was higher than along the ⟨100⟩ direction and anomalous, two-step-structure elastic waves were observed. These characteristics are discussed based on the slip system of the MgO crystal.