Kinetics of phase separation in binary fluids: Nucleation near the critical point

Recent interest in the nucleation problem has been stimulated, at least in part, by a sharp disagreement between conventional droplet theories and observations of anomalously large supersaturations in binary fluids near their critical points1–5). This problem apparently has been resolved by examining actual completion rates instead of focusing attention only on rates of droplet formation6,7). Current calculations are in reasonable agreement with observed cloud points, but more detailed predictions of average sizes and numbers of droplets as functions of time after quench have not yet been checked by experiment. One outstanding theoretical problem is that of joining the early state nucleation theory to the late stage theory of coarsening. An improved analysis of this transition will be necessary in order to make accurate predictions of the size distribution of droplets throughout the reaction. It also will be necessary to generalize the Lifshitz-Slyozov-Wagner8,9) theory of coarsening to account for finite volume fractions of the nucleating phase, especially if one wants to extend the theory to describe the relatively deep quenches achieved near the critical point.