Drop Model and Classical Nucleation Theory

It is clear from Table 1 and Fig. 9 that classical nucleation theory, based on the drop model, does not yield complete agreement with experiment. Before proceeding to the various attempts to improve on classical nucleation theory, it is desirable to understand why it fails. There are two basic types of criticisms, which we will now discuss. 

We noted before that classical nucleation theory uses Eq. (41) to calculate cluster concentrations, rather than Eq. (36). Obviously this is incorrect. As the monomer concentration hi is of the order of 10, this error will introduce a factor of 10 in the nucleation rate. 

In addition, in writing Eq. (38) for AF(i) we have implicitly neglected the rotational and translational contributions to the partition function of the cluster. The total partition function of the cluster should be written 

The argument used in arriving at the drop model expression for the cluster free energy [Eq. (38)] did not include any mention of rotation and translation. 

Tolman also noted another problem with the drop model. It is really derived from continuous thermodynamics and so implicitly assumes that the 

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