Phase behaviour of a symmetrical binary mixture in a field

¹ Faculty of Physics, University of Vienna - Boltzmanngasse 5, 1090 Vienna, Austria
² Institut für Theoretische Physik and Center for Computational Materials Science TU Wien - Wiedner Hauptstraße 8-10, A-1040 Wien, Austria
³ Department of Physics, University of Bath - Bath BA2 4LP, UK

Received: 13 February 2006
Accepted: 22 May 2006

Abstract

Integral equation theory calculations within the mean spherical approximation (MSA) and grand canonical Monte Carlo (MC) simulations are employed to study the phase behaviour of a symmetrical binary fluid mixture in the presence of a field arising from unequal chemical potentials of the two particle species. Attention is focused on the case for which, in the absence of a field, the phase diagram exhibits a first-order liquid-liquid transition in addition to the liquid-vapor transition. We find that in the presence of a field, two possible subtypes of phase behaviour can occur, these being distinguished by the relationship between the critical lines in the full phase diagram of temperature, density, and concentration. We present the detailed form of the respective phase diagrams as calculated from MSA and compare with results from the MC simulations, finding good overall agreement.