Role of constraints in the thermodynamics of heterogeneous condensation onsolid soluble particles: failure of the capillarity approximation

The Debenedetti-Reiss method of using constraints in the derivation of the reversible work of nucleus formation is extended to the case of heterogeneo us formation of multicomponent liquid droplets on solid (soluble or insolub le) particles. It is shown that not only does the capillarity approximation fail to predict the complete, true free energy of formation of a drop of a rbitrary (i.e., nonequilibrium) size, but it may also fail to provide a wel l behaved "surrogate" free energy which would not depend on the path of for mation of the drop. This failure is illustrated by calculating the free ene rgy of formation of a liquid film on a NaCl-like particle. (C) 2001 Elsevie r Science B.V. All rights reserved.