Thermoelastic equation of state and melting of Mg metal at high pressure and high temperature

摘要

The p-V-T equation of state of magnesium metal has been measured up to 20 GPa and 1500 K using both multianvil and opposite anvil techniques combined with synchrotron x-ray diffraction. To fit the experimental data, the model of Anderson-Griineisen has been used with fixed parameter δ_T. The 300-K bulk modulus of B_0 = 32.5(1) GPa and its first pressure derivative, B_0' = 3.73(2), have been obtained by fitting available data up to 20 GPa to the Murnaghan equation of state. Thermal expansion at ambient pressure has been described using second order polynomial with coefficients a = 25(2) × 10~(-6) K~(-1) and b = 9.4(4) × 10~(-9) K~(-2). The parameter describing simultaneous pressure and temperature impact on the thermal expansion coefficient (and, therefore, volume) is δ_T= 1.5(5). The good agreement between fitted and experimental isobars has been achieved to relative volumes of 0.75. The Mg melting observed by x-ray diffraction and in situ electrical resistivity measurements confirms previous results and additionally confirms the p-T estimations in the vicinity of melting.