Investigation of equation-of-state and melting behavior of rhodium up to 200 GPa

Abstract

Equation-of-state (EOS) of face-centered cubic rhodium is studied using the moment method in statistical mechanics. Numerical calculations for rhodium metal have been implemented up to 200 GPa, and the bulk modulus $K_0$ and its first pressure derivative $K_1$ have been derived by fitting our EOS prediction with the Birch-Murnaghan and Vinet EOSs. The Vinet EOS fit yields parameters $K_0=244.57$ GPa and $K_1=5.50$, while the Birch-Murnaghan EOS fit gives $K_0=251.08$ GPa and $K_1=5.07$. Furthermore, the pressure-dependent melting curve of rhodium has been investigated using the Force-Heat Equivalence Energy Density Principle approach, along with the obtained $K_0$ and $K_1$. Our theoretical melting curve shows good agreement with ab initio one-phase calculations up to 90 GPa. The theoretical melting curve of rhodium is accurately described by the Simon-Glatzel equation as $T_m={(1+P/21.8742)}^{0.4891}$.