Thermodynamic properties of mixtures of dipolar and quadrupolar hard spheres: Theory and simulation

Abstract

We report a comprehensive study of the thermodynamic properties (the Helmholtz energy, configurational energy, compressibility factor, and chemical potentials) for mixtures of dipolar hard spheres and quadrupolar hard spheres by computer simulation and from perturbation theory based on the Padé approximation. The dipole moment of dipolar component is fixed at μA*2=3.0 and the quadrupole moment of quadrupolar component is varied up to QB*2=3.0. The results show that the Padé approximation gives a good description of the Helmholtz energy and configuration energy of the mixtures, but some discrepancies are found for their derivatives, especially for compressibility factor. In view of very large deviations for the system from simple mixtures, the Padé approximation is rather successful for the system. These results are being used as a reference system in our effort to develop an equation of state for the CaCl2–H2O system.