Global phase diagrams of binary dipolar fluid mixtures

Abstract

We apply a modified mean-field density functional theory to determine the phase behavior of binary mixtures of Stockmayer fluids whose spherical constituents interact according to Lennard-Jones (LJ) pair potentials with embedded pointlike dipole moments. On the basis of systematic numerical calculations we construct the global phase diagrams of these systems in the three-dimensional thermodynamic space of temperature, pressure, and chemical potential difference of the two components. The vapor-liquid, isotropic liquid -isotropic liquid, isotropic liquid -ferromagnetic liquid, and ferromagnetic liquid -ferromagnetic liquid first-order phase separations are investigated. The loci of the second-order isotropic fluid -ferromagnetic fluid transition are calculated from Landau theory. Liquid-vapor and liquid-liquid critical lines, tricritical lines, triple lines, and lines of critical end points of the binary Stockmayer mixtures are also determined. We discuss how the topology of the phase diagrams change upon varying the strengths of the two dipole moments of the two species as well as their sizes.

Phase transitions and ordering of confined dipolar fluids

“…The phase diagrams exhibit the usual liquid-gas critical point, a triple point, a tricritical point, and a line of critical points corresponding to second-order phase transitions between the isotropic and the ferromagnetic liquid. For bulk dipolar fluids these phase transitions and critical points and lines have been detected in various theoretical studies [12][13][14][15][16].…”

Fundamental measure density functional theory studies on the freezing of binary hard-sphere and Lennard-Jones mixtures

“…23 Our method can also be extended to study the solidliquid phase equilibria of mixtures with molecules interacting via the angle-dependent potentials, such as LJ dumbbells 37 or Stockmayer molecules. 38,39 Applications of the method to metallic alloys with embedded-atom model potentials are also very promising. 40 Since within our approach the solid and liquid mixtures are treated using a single theoretical method it may be possible to apply this approach to investigate the interface between solid and liquid mixtures.…”

Electric field dependence of phase equilibria of binary Stockmayer fluid mixtures

“…[7,8] for a review) for the calculation of thermal properties of dipolar fluid mixtures, even if we restrict the question to the vaporliquid and liquid-liquid equilibria [9]. Among them, perturbation theory is quite adequate to determine the main effect caused by the dipole-dipole interaction on one hand, and by the electric field on the other.…”