Supercritical Crossover Lines in the Cell Fluid Model

TL;DR

This paper investigates supercritical crossover lines in a cell fluid model with a modified Morse potential, identifying key thermodynamic boundaries that distinguish liquid-like and gas-like behaviors.

Contribution

It introduces three specific lines in the supercritical region that serve as boundaries between different fluid behaviors, based on thermodynamic maxima and an effective chemical potential condition.

Findings

Identified the locus of isothermal compressibility maxima.

Determined the line of thermal expansion coefficient maxima.

Established the M=0 line as an analog to the absence of external field in the Ising model.

Abstract

A cell fluid model with a modified Morse potential is studied. The supercritical states are considered with respect to a possibility to build a separation boundary between liquid-like and gas-like bahaviors. Three different lines are calculated that can be used for this purpose: the locus of the isothermal compressibility maxima, the locus of the thermal expansion coefficient maxima, and the line where the effective chemical potential is zero, M=0. By the symmetry of the functionals for the partition functions, the condition M=0 in fluids is analogous to the absence of an external field in the Ising model.