Molecular theory of ultramicro clusters and nucleation. i. the surface free energy

Abstract

In the process of nucleation, single molecules of a mother phase gather, grow, and form macroscopic particles of the new phase. Therefore, clarification of the surface properties of the clusters at the early stage of the nucleation process or the ultramicro clusters should provide the crucial information for the process. By thermodynamically clarifying that the surface free energy, σ, is a normal surface potential, the size dependence is estimated with the help of a rigid sphere, pair-wise attractive intermolecular potentials. For large clusters, the model results agreed with the Tolman equation in tendency but for ultramicro clusters, the result of the nearest neighbor interaction model became much smaller for the dimer, by a factor of 10. When the long range interaction was considered, the factor became about 30. The estimated σ behavior of ultramicro clusters indicates σ = 0 at monomer, which the Tolman equation does not.