Thermodynamics of the insulator-metal transition in dense liquid deuterium

TL;DR

This paper investigates the thermodynamics of the insulator-metal transition in dense liquid deuterium, challenging previous claims of large latent heat effects and providing new computational insights into the transition's temperature behavior.

Contribution

The study uses path-integral molecular dynamics with density functional theory to directly assess latent heat effects, refuting prior suggestions of significant temperature drops during the transition.

Findings

Large latent heat effects are inconsistent with thermodynamics.

The insulator-metal transition does not cause a significant temperature drop.

Previous pressure discrepancies are not explained by latent heat effects.

Abstract

Recent dynamic compression experiments [M. D. Knudson et al., Science 348, 1455 (2015); P. M. Celliers et al., Science 361, 677 (2018)] have observed the insulator-metal transition in dense liquid deuterium, but with an approximately 95 GPa difference in the quoted pressures for the transition at comparable estimated temperatures. It was claimed in the latter of these two papers that a very large latent heat effect on the temperature was overlooked in the first, requiring correction of those temperatures downward by a factor of two, thereby putting both experiments on the same theoretical phase boundary and reconciling the pressure discrepancy. We have performed extensive path-integral molecular dynamics calculations with density functional theory to directly calculate the isentropic temperature drop due to latent heat in the insulator-metal transition for dense liquid deuterium and show that this large temperature drop is not consistent with the underlying thermodynamics.