Compressional sound velocity, equation of state, and constitutive response of shock-compressed magnesium oxide

Wave profile and equation of state (EOS) data are reported for low-porosity polycrystalline magnesium oxide under shock compression. The Hugoniot equation of state between 14 and 133 GPa is U_S = 6.87(10) + 1.24(4)u_p, where the numbers in parentheses are one standard deviation uncertainties in the last digit(s). Reverse-impact wave profiles constrain the compressional sound velocity, V_P, at 10-27 GPa to ±2%. By combining the Hugoniot results with ultrasonic data, the adiabatic bulk modulus and its first and second pressure derivatives at constant entropy are 162.5(2) GPa, 4.09(9), and -0.019(4) GPa^-1. Polycrystalline MgO has a compressive yield strength of 1-1.5 GPa at the elastic limit which increases to 2.7(8) GPa along the Hugoniot and is similar at unloading. Wave profiles for MgO at 10-39 GPa are described using a modified elastic-plastic model. -from Authors