Condensed Matter Physics, 2014, vol. 17, No. 4, 43004
DOI:10.5488/CMP.17.43004           arXiv:1408.5755

Title: Gas-liquid phase equilibrium in ionic fluids: Coulomb versus non-Coulomb interactions
  O. Patsahan (Institute for Condensed Matter Physics of the National Academy of Sciences of Ukraine, 1 Svientsitskii St., 79011 Lviv, Ukraine)

Using the collective variables theory, we study the effect of competition between Coulomb and dispersion forces on the gas-liquid phase behaviour of a model ionic fluid, i.e. a charge-asymmetric primitive model with additional short-range attractive interactions. Both the critical parameters and the coexistence envelope are calculated in a one-loop approximation as a function of the parameter α measuring the relative strength of the Coulomb to short-range interactions. We found the very narrow region of α bounded from the both sides by tricritical points which separates the models with "nonionic" and "Coulombic" phase behaviour. This is at variance with the result of available computer simulations where no tricritical point is found for the finely-discretized lattice version of the model.

Key words: ionic fluids, gas-liquid phase diagram, tricritical point, Coulomb interactions, short-range attraction
PACS: 05.70.Fh, 64.60.De, 64.60.Kw

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