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Liquid-vapor interface of an ionic fluid

B. Groh1, R. Evans1,2, and S. Dietrich1

  • 1Fachbereich Physik, Bergische Universität Wuppertal, D-42097 Wuppertal, Federal Republic of Germany
  • 2H.H. Wills Physics Laboratory, University of Bristol, Bristol BS8 1TL, United Kingdom

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Phys. Rev. E 57, 6944 – Published 1 June, 1998

DOI: https://doi.org/10.1103/PhysRevE.57.6944

Abstract

We investigate the liquid-vapor interface of the restricted primitive model (RPM) for an ionic fluid using a density-functional approximation based on correlation functions of the homogeneous fluid as obtained from the mean-spherical approximation. The ionic interfacial density profiles, which for the RPM are identical for both species, have a shape similar to those of simple atomic fluids in that the decay towards the bulk values is more rapid on the vapor side than on the liquid side. This is the opposite asymmetry of the decay to that found in earlier calculations for the RPM based on a square-gradient theory. The width of the interface is, for a wide range of temperatures, approximately four times the second moment correlation length of the liquid phase. We discuss the magnitude and temperature dependence of the surface tension and argue that for temperatures near the triple point the ratio of the dimensionless surface tension and critical temperature is much smaller for the RPM than for simple atomic fluids.

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Phys. Rev. E 57, 6944– Published 1 June, 1998
  • Received 30 October 1997

© 1998 American Physical Society

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