Local structure of supercritical matter

TL;DR

This study investigates the local structure of supercritical matter across wide temperature ranges, revealing a structural crossover linked in reciprocal and real spaces, with implications for experimental detection and industrial applications.

Contribution

It provides the first comprehensive analysis connecting structural crossover phenomena in reciprocal and real spaces of supercritical fluids.

Findings

Monotonic disappearance of medium-range order correlations at high temperatures

Structural crossover in reciprocal space is linked to real space changes

Implications for detecting structural transitions experimentally

Abstract

The supercritical state is currently viewed as uniform on the pressure-temperature phase diagram. Supercritical fluids have the dynamic motions of a gas but are able to dissolve materials like a liquid. They have started to be deployed in many important industrial applications stimulating fundamental theoretical work and development of experimental techniques. Here, we have studied local structure of supercritical matter by calculating static structure factor, mean force potential, self-diffusion, first coordination shell number and pair distribution function within very wide temperature ranges. Our results show a monotonic disappearance of medium-range order correlations at elevated temperatures providing direct evidence for structural crossover in the reciprocal and real spaces. Importantly, the discovered structural crossover in the reciprocal space is fundamentally inter-related to structural crossover in the real space, granting new unexpected interlinks between operating system properties in the supercritical state. Finally, we discuss an evolution analysis of the local structure and important implications for an experimental detection of structural monotonic transitions in the supercritical matter.