Modeling the thermodynamic properties and determination of the melting curve of Rhodium at high temperatures and pressures

Abstract

This article presents an in-depth study of the thermodynamic and melting properties of rhodium metal with a face-centered cubic (FCC) structure under extreme temperatures and pressures. Using the statistical moment method (SMM), key structural and thermodynamic characteristics such as lattice constant, volume, thermal expansion coefficient and isobaric heat capacity are calculated at temperatures up to 2000 K and pressures up to 500 GPa taking into account the anharmonic contribution of the crystal lattice vibrations. The SMM calculations are compared with available experimental data and other theoretical results. We find that in the high temperature region, the influence of anharmonic lattice vibrations at pressure does not break the classical limit of isobaric heat capacity. The sharp decrease in thermal expansion coefficient at high pressure demonstrates dynamic stability at 300 GPa. We build the Vinet equation with the obtained parameters $V_0=$ $13.867{\AA }^3,K_0=249.54\text{GPa},K_0^{\prime }=5.45$ combined with the heat-work equivalence principle (WHEP) to describe the melting curve for rhodium up to 500 GPa. This study provides an effective theoretical approach to investigate the structural and thermodynamic properties together with melting curve of strong anharmonic materials under extreme conditions. Our research results will provide useful information on the thermodynamic and melting properties of Rh as reinforcing agents in high-temperature thermocouples.