INFLUENCE OF STATIC ELECTRIC-FIELD ON THE VAPOR-LIQUID COEXISTENCE OFDIPOLAR SOFT-SPHERE FLUIDS

The influence of a static homogeneous electric field on the vapour-liq uid equilibrium of dipolar soft-sphere fluids has been studied by the Gubbins-Pople-Stell perturbation theory. The thermodynamic properties of the fluid as functions of the field strength were derived from the Helmholtz energy containing the field-dependent relative permittivity. The dielectric saturation was studied by a perturbation theoretical t reatment of the Kirk-wood equation. Our calculations can yield a weak negative saturation. It was found that the critical quantities increas e, while the temperature range;of the phase coexistence narrows with t he field strength. A comparison between our electrostriction results a nd simulation data shows reasonable agreement at low field strengths.