Failure of the constrained equilibrium hypothesis in nucleation.

The purpose of this investigation is to find whether solutions of the Becker-Doring-Tunitskii coupled differential equations can yield results closely paralleling those found in molecular dynamics (MD) simulations of freezing. What is investigated, in particular, is the validity of the constrained equilibrium hypothesis (CEH). It is shown that the MD results cannot be reproduced unless the CEH is violated. A physically plausible reason for the violation is proposed. In addition, methods for determining the size of critical nuclei are examined. It is found that a new criterion for identifying that size, a criterion incorporating the CEH, can be significantly in error. Methods for avoiding the use of the CEH are briefly discussed.