Percolation line and response functions in simple supercritical fluids

Abstract

The question of a physical relevance (meaning) of the percolation line in simple supercritical fluids has been addressed using both extensive Monte Carlo simulations and accurate analytic equations of state. Thermodynamic and structural properties of two qualitatively different fluids, the Lennard-Jones (continuous model) and square-well fluid (stepwise model), have been studied in the vicinity of their percolation lines over a range of pressures in order to find potential changes which may take place when an infinite cluster is detected in the system. Two different criteria for the occurrence of an infinite cluster, physical and configurational criteria, have also been used to assess their effect on the observed properties. It is found that the lines of extremes of various response functions run close to the percolation lines. Accounting for uncertainties in the definition of bonds and determination of the percolation line one may conjecture that extremes in some response functions occur when crossing the percolation line.

Keywords:

• percolation line
• response functions
• supercritical fluids

Acknowledgements

This work was supported by the Grant Agency of the Academy of Sciences of the Czech Republic (Grant No.\ IAA200760905) and by the Internal Grant Agency of the J. E. Purkinje University (Grant No. 53223∼15∼0010∼01)