Thermodynamic Quantities of Morse Fluids in the Supercritical Region


  • I.V. Pylyuk Institute for Condensed Matter Physics, Nat. Acad. of Sci. of Ukraine
  • M.P. Kozlovskii Institute for Condensed Matter Physics, Nat. Acad. of Sci. of Ukraine
  • O.A. Dobush Institute for Condensed Matter Physics, Nat. Acad. of Sci. of Ukraine



Morse interaction potential, critical point, thermodynamic potential, isothermal compressibility, density fluctuations, thermal expansion


The critical point parameters for liquid alkali metals (sodium and potassium) are calculated accounting for the non-Gaussian order parameter fluctuations and the Morse interaction potential. The behavior of the isothermal compressibility, density fluctuations, and thermal expansion for sodium is studied in the supercritical temperature region. A significant increase in the isothermal compressibility and the density fluctuations near the critical point indicates a substantial density sensitivity to tiny pressure fluctuations. The thermal expansion coefficient for various fixed pressure values shows a typical gas decrease with increasing supercritical temperature. The Widom line separating the gaseous and liquid structures of the fluid at temperatures above the critical one is represented. Note that our calculations are valid in a small neighborhood of the critical point, which is problematic for theoretical and experimental studies.


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How to Cite

Pylyuk, I., Kozlovskii, M., & Dobush, O. (2023). Thermodynamic Quantities of Morse Fluids in the Supercritical Region. Ukrainian Journal of Physics, 68(6), 383.



Physics of liquids and liquid systems, biophysics and medical physics