| Abstract: | Among the assumptions in the derivation of the classical nucleation equations has been important that of the independence of the interfacial tension on the critical size of the two-dimensional nucleus. The one layer adsorption model based on Bragg-Williams approximation with empty sites has been used to investigate the dependence of interfacial tension on the number of molecules in the square shaped critical nucleus. Using the Gibbs adsorption at constant temperature for a two-component system, the number of molecules in the critical nucleus is exactly calculated in terms of the supersaturation, the interfacial tension and the interaction energies between the adsorbed molecules. The correction for the free energy of formation of critical two-dimensional nucleus due to the new term associated with the dependence of the interfacial tension on cluster size is derived. Assuming the correction term for the free energy is negligibly small, the expression for the variation of interfacial tension of an embryo from that of a plane surface is established. It is found that the deviation is significant for small clusters and decreases with increase in the size of thejnucleus. |
