Simulation and extrapolation of coexistence properties with single-phase and two-phase ensembles

A unified framework is developed to describe extrapolations from simulation s performed in either a single system box or two subsystems at equilibrium (i.e., Gibbs ensembles). It is shown that the Gibbs ensemble can be used in conjunction with histogram reweighting and pseudo-ensemble techniques in o rder to map out more effectively different kinds of phase diagrams, in part icular for binary and ternary systems. These extrapolation schemes allow th e use of different phase-equilibrium specifications, some of which could no t be simulated by conventional approaches. Novel semi-open and osmotic Gibb s ensembles are also described as counterparts of single-phase open and osm otic ensembles, respectively. Applications of the proposed methods are pres ented to the simulation of pressure-composition diagrams, bubble lines, and isoenthalpic partitioning. (C) 2000 American Institute of Physics. [S0021- 9606(00)51743-7].