Precise simulation of criticality in asymmetric fluids

Extensive grand canonical Monte Carlo simulations have been performed for the hard-core square-well fluid with interaction range (Formula presented) The critical exponent for the correlation length has been estimated in an unbiased fashion as (Formula presented) via finite-size extrapolations of the extrema of properties measured along specially constructed, asymptotically critical loci that represent pseudosymmetry axes. The subsequent location of the critical point achieves a precision of five parts in (Formula presented) for (Formula presented) and about 0.3% for the critical density (Formula presented) The effective exponents (Formula presented) and (Formula presented) indicate Ising-type critical-point values to within 2% and 5.6%, respectively, convincingly distinguishing the universality class from the “nearby” XY and (Formula presented) (self-avoiding walk) classes. Simulations of the heat capacity (Formula presented) and (Formula presented) where (Formula presented) is the vapor pressure below (Formula presented) suggest a negative but small Yang-Yang anomaly, i.e., a specific-heat-like divergence in the corresponding chemical potential derivative (Formula presented) that requires a revision of the standard asymptotic scaling description of asymmetric fluids.