For Noble Gases, Energy is Positive for the Gas Phase, Negative for the Liquid Phase

TL;DR

This paper analyzes experimental data to show that noble gases and hydrogen have positive energy in the gas phase and negative in the liquid phase, with the transition near the Widom line close to the critical point.

Contribution

It identifies the energy sign change across phases and links the supercritical energy line to the Widom line, providing new insights into phase behavior.

Findings

Energy is positive in the gas phase and negative in the liquid phase for noble gases and H2.

The transition occurs near the critical point, within 0.5% of T_c.

The supercritical energy line aligns with the Widom line.

Abstract

We found from experimental data that for noble gases and H$_2$, the energy is positive for the gas phase, and negative for the liquid, possibly except the small vicinity of the critical point, about $(1- T/T_c) \le 0.005$. The line $E=E_c$, in the supercritical region is found to lie close to the Widom line, where $E_c$ is the critical energy.