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

TL;DR

This study measures the equation of state and melting behavior of magnesium metal at high pressures and temperatures, providing new data and confirming previous melting point estimations through X-ray and resistivity methods.

Contribution

It presents comprehensive high-pressure, high-temperature data for magnesium's equation of state and melting point, using advanced experimental techniques and modeling.

Findings

Bulk modulus at 300 K is 32.5 GPa

Thermal expansion coefficients are quantified

Melting confirmed near previous estimations

Abstract

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-Gr\"uneisen has been used with fixed parameter {\delta}T. The 300-K bulk modulus of B0 = 32.5(1) GPa and its first pressure derivative, B0' = 3.73(2), have been obtained by fitting available data up to 20 GPa to Murnaghan equation of state. Thermal expansion at ambient pressure has been described using second order polynomial with coefficients a = 25(2)x10-6 K-1 and b = 9.4(4)x10-9 K-2. The parameter describing simultaneous pressure and temperature impact on thermal expansion coefficient (and, therefore, volume) is {\delta}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.