Refinement of the equation of state of tantalum

TL;DR

This study provides precise measurements of tantalum's volume under high pressure, revealing discrepancies with previous data and raising questions about pressure calibration methods, supported by first-principles calculations.

Contribution

It offers new high-precision experimental data on tantalum's equation of state and critically compares it with existing models and calibration scales.

Findings

Accurate volume measurements up to 101 GPa

Discrepancies with previous static and shock-wave data

Support for doubts about ruby pressure scale calibration

Abstract

The volume of tantalum versus pressure has been accurately measured up to 101 GPa by single-crystal x-ray diffraction, with helium as pressure transmitting medium. Slight deviation from previous static determinations is observed. Discrepancy with reduced shock-wave and ultrasonic data supports recent doubts about the calibration of the ruby pressure scale. Finally, first principle calculations of the literature show a positive curvature in $P(V)$ relative to the experimental data, even with a modified pressure scale.