We continue our investigation of the properties of a model fluid whose molecules have classical translational degrees of freedom and two quantum internal states. The attractive pair interactions are ‘‘turned on’’ when the internal states are hybridized, corresponding to the molecules acquiring a ‘‘dipole’’ moment. The phase diagram of this system in the temperature-density plane as well as the static and imaginary-time correlations at various densities are investigated by Monte Carlo simulations, using the ‘‘polymer’’ representation, for different strengths of the quantum parameter. These are compared with low-density expansions and mean-field-theory predictions. Good agreement is found in appropriate regimes.

• Received 11 December 1987

DOI:https://doi.org/10.1103/PhysRevA.38.1381