International Journal of Thermophysics

, Volume 35, Issue 9–10, pp 1770–1784 | Cite as

Gibbs Density Surface of Fluid Argon: Revised Critical Parameters

  • Leslie V. Woodcock


A phase diagram of simple fluids, based upon percolation transition loci determined from literature experimental density-pressure isotherms of argon, shows three fluid phases. The liquid phase spans all temperatures from a metastable amorphous ground state to supercritical temperatures. There is a supercritical mesophase of a colloidal nature between two percolation transition loci, PA and PB, that bound the existences of liquid and gas phases, respectively. There is no ‘critical point’ on the Gibbs density surface. When two percolation transitions have the same pressure, i.e., on intersection of the loci in the \(p\)\(T\) plane, an equilibrium ‘line of critical states’ is thermodynamically defined. This description of criticality yields slightly different values of critical parameters than those hitherto obtained by interpolation of experimental \(p\)\(\rho \)\(T\) data from the coexistence region. Revised values of the critical temperature (\(T_\mathrm{c})\) and critical pressure (\(p_\mathrm{c})\) of argon can be obtained from the original high precision thermodynamic measurements for fluid argon, using only data from one-phase supercritical isotherms. Values of coexisting densities at \(T_\mathrm{c}\) and the density loci of the percolation transitions that bound the existence of supercritical gas and liquid phases for \(T>T_\mathrm{c}\) are also reported. Percolation loci, for \(T<T_\mathrm{c}\), extend into the gas–liquid coexistence region to become the spinodal lines that limit the existence of metastable gas and liquid phases.


Argon Critical point Gas–liquid coexistence Percolation transition  



We wish to acknowledge KAUST (Korean Association of Universities of Science and Technology) for a visiting research award under the auspices of the S. Korean Brain-Pool Scheme which enabled completion of this work and attendance at the 18th Symposium on Thermophysical Properties: June 2012. Helpful discussions with Professor Sang Rak Kim (Kyonggi University), Professor David Heyes (London University), and Drs. John F. Maguire and Frank van Swol (Scientific Simulation Systems Inc.) are gratefully acknowledged


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Copyright information

© Springer Science+Business Media New York 2013

Authors and Affiliations

  1. 1.Manchester Interdiciplinary BiocentreUniversity of ManchesterManchesterUK

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