Phase Transition and Chain Formation in Dipolar Fluids

Gibbs ensemble simulations are reported for the Lennard-Jones potential with embedded dipoles and quadrupoles of varying strengths. The reduced dipole moments ranged from 0.1 to 0.5 and the reduced quadrupole moments had values ranging from 0.1 to 5.0. The simulation data are analyzed to estimate the critical properties of the polar fluid, vapor-liquid coexistence and their dependence on the strength, λ, of the dispersive force. Chain formation is observed for the dipole in both phases to a degree that depends on the number density and strength of the dipolar interactions. Our simulation results clearly indicate that one can get vapor-liquid coexistence in the presence of quadrupole moments even at the smallest value of λ.