On the thermodynamic driving force for interpretation of nucleation experiments

According to the Classical Nucleation Theory (CNT), the volume and surface thermodynamic properties of the nuclei of a new (nucleating) phase are considered to be size independent and hence equal to the respective values of the corresponding macroscopic crystals. However, this assumption leads (if one also considers in addition σ as temperature independent) to a dramatic underestimation of steady-state nucleation rates. In this paper, we propose as a resolution of these problems that one should employ a value of the thermodynamic driving force that is equal to that for formation of macroscopic crystals, but reduced by a constant value. This approach leads to a considerable decrease in the thermodynamic barrier for nucleation. This choice of the thermodynamic driving force for the analysis of nucleation rate data employing the classical equation results in a self-consistent description that allows one not only to obtain the theoretically expected value of the size of the structural units and of the pre-exponential term in the steady-state nucleation rate equation, but also to obtain a more reliable (reduced) value of the crystal/melt interfacial energy than that estimated in the framework of currently utilized CNT approximations.