Activation barrier for multicomponent droplet formation on partially soluble nuclei

We present a thermodynamic treatment for obtaining the free energy surface as a function of droplet composition as well as the activation barrier for droplet formation in a multicomponent vapor mixture on a nucleating center which consists of both an insoluble core and some soluble species. An exten sion of Kuni's method [Kuni et al,, 1993a] of studying the free energy of d roplet formation to heterogeneous multicomponent condensation makes it poss ible to find all the main features of the free energy surface without expli citly knowing the free energy itself. Using that method, we obtain the ineq ualities that serve as criteria for whether heterogeneous condensation is b arrierless or occurs in a fluctuational way or does not occur at all. An ex plicit expression for the height of the activation barrier for heterogeneou s multicomponent condensation on mixed nuclei is proposed. The theoretical results are illustrated by numerical calculations for condensation on mixed nuclei in the water-methanol and water-sulfuric acid systems.