An approach for calculating the free energy of embryo formation for multicomponent heterogeneous nucleation has been developed. The approach is based a differential version of the capillarity approximation. It is considered that a liquid droplet is formed due to the deposition of several gaseous compounds onto a nucleolus containing a spherical insoluble core and nonvolatile soluble substances. The approach links interfacial free energies of the surfaces, the size of the insoluble core, and chemical characteristics of the substances with the free energy of the embryo formation. The free energy of embryo formation as well as the critical supersaturation are influenced by the ration of the Henry's Law constants to the partial pressures of the species. Multicomponent nucleation with a dominant species can be described as a quasibinary nucleation of the dominant species and a virtual species. As an example, the free energy in a binary system of water and acid is considered. It is shown that water+acid nucleation on such nuclei is influenced by the acid, soluble nonvolatile compounds and insoluble substances.
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