  Fluid phase behavior of charge-stabilized colloidal suspensions is explored
by applying a new variant of the Gibbs ensemble Monte Carlo simulation method
to a coarse-grained one-component model with implicit microions and solvent.
The simulations take as input linear-response approximations for effective
electrostatic interactions -- hard-sphere-Yukawa pair potential and one-body
volume energy. The conventional Gibbs ensemble trial moves are supplemented by
exchange of (implicit) salt between coexisting phases, with acceptance
probabilities influenced by the state dependence of the effective interactions.
Compared with large-scale simulations of the primitive model, with explicit
microions, our computationally practical simulations of the one-component model
closely match the pressures and pair distribution functions at moderate
electrostatic couplings. For macroion valences and couplings within the
linear-response regime, deionized aqueous suspensions with monovalent microions
exhibit separation into macroion-rich and macroion-poor fluid phases below a
critical salt concentration. The resulting pressures and phase diagrams are in
excellent agreement with predictions of a variational free energy theory based
on the same model.
