Condensed Matter Physics, 2012, vol. 15, No. 2, p. 23301:1-8
DOI:10.5488/CMP.15.23301           arXiv:1207.3263

Title: Percolation line, response functions, and Voronoi polyhedra analysis in supercritical water
  J. Škvor (Faculty of Science, J.E. Purkinje University, 400 96 Ústí nad Labem, Czech Republic) ,
  I. Nezbeda (Faculty of Science, J.E. Purkinje University, 400 96 Ústí nad Labem, Czech Republic; Institute of Chemical Process Fundamentals, Academy of Sciences, 165 02 Prague 6, Czech Republic)

The problem of a physical relevance (meaning) of percolation in supercritical fluids is addressed considering a primitive model of water. Two different criteria, physical and configurational, are used for the cluster definition in Monte Carlo simulations over a range of pressures to determine the percolation line and skewness, and a theoretical analytic equation of state is used to evaluate response functions. It is found that both criteria yield practically the same percolation line. However, unlike the findings for simple fluids, the loci of the response function extrema exhibit density/pressure dependence quite different from that of the percolation line. The only potential coincidence between the loci of the extrema of a thermodynamic property and a detectable structural change is found for the coefficient of isothermal compressibility and Voronoi neighbors distribution skewness maximum.

Key words: percolation line, response functions, Widom lines, supercritical water, Voronoi tessellation
PACS: 36.40

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