Melting of tantalum under high pressure: <i>in situ</i> x-ray diffraction and <i>ab initio</i> molecular dynamic simulations

Abstract

The melting behavior of tantalum under high pressure is of fundamental importance to materials science and high-energy-density applications. In this study, we investigated tantalum up to 450 GPa by combining in situ x-ray diffraction with ab initio molecular dynamics (AIMD) simulations. Our experiments provide direct evidence that the body-centered cubic phase is retained from ambient conditions to 318 GPa. This conclusion is supported by the observation of multiple diffraction peaks, including Ta(110), Ta(200), and Ta(211). Our findings on the crystal structure are consistent with those reported by recent work [Phys. Rev. Lett. 126, 255701 (2021)]. The melting curve was derived from AIMD simulations based on density functional theory, without the use of empirical potentials. The obtained melting curve shows good agreement with earlier reliable first-principles theoretical studies, suggesting the limitations of empirical models over broad pressure and temperature ranges. Our combined experimental and computational approach provides a robust framework for studying high-pressure melting in refractory metals and is broadly applicable to materials subjected to extreme environments.