Sound velocity measurements of tantalum under shock compression in the 10-110 GPa range

TL;DR

This study measures sound velocities of tantalum under shock compression up to 110 GPa to investigate its high-pressure melting behavior, revealing a potential structural or electronic transition near 60 GPa.

Contribution

It provides new experimental data on sound velocities of tantalum under shock compression, aiding understanding of its high-pressure phase transitions.

Findings

Longitudinal sound velocity shows a kink at ~60 GPa.

Bulk sound velocity remains continuous across the pressure range.

Results suggest a structural or electronic transition in tantalum.

Abstract

The high-pressure melting curve of tantalum (Ta) has been the center of a long-standing controversy. Sound velocities along the Hugoniot curve are expected to help in understanding this issue. To that end, we employed a direct-reverse impact technique and velocity interferometry to determine sound velocities of Ta under shock compression in the 10-110 GPa pressure range. The measured longitudinal sound velocities show an obvious kink at ~60 GPa as a function of shock pressure, while the bulk sound velocities show no discontinuity. Such observation could result from a structural transformation associated with a negligible volume change or an electronic topological transition.