Liquid–vapor asymmetry in pure fluids: A Monte Carlo simulation study

Monte Carlo simulations within the grand canonical ensemble are used to obtain the joint distribution of density and energy fluctuations pL(ρ,u) for two model fluids: a decorated lattice gas and a polymer system. In the near critical region the form of pL(ρ,u) is analyzed using a mixed field finite‐size‐scaling theory that takes account of liquid–vapor asymmetry. Field mixing transformations are performed that map pL(ρ,u) onto the joint distribution of critical scaling operators p=(x,y) appropriate to the Ising fixed point. Carrying out this procedure permits a very accurate determination of the critical point parameters. By forming various projections of p=(x,y), the full universal finite‐size spectrum of the critical density and energy distributions of fluids is also obtained. In the sub‐critical coexistence region, an examination is made of the influence of field mixing on the asymmetry of the density distribution.