 Most fundamentally, in the so-called "capillarity approximation" it treats the nucleus interior as a bulk, incompressible fluid and ascribes to the nucleus surface the "macroscopic" interfacial tension formula_49, even though it is not obvious that such macroscopic equilibrium properties apply to a typical nucleus of, say, 50 molecules across.In fact, it has been shown that the effective surface tension of small droplets is "smaller" than that of the bulk liquid.In addition, the classical theory places restrictions on the kinetic pathways by which nucleation occurs, assuming clusters grow or shrink only by single particle adsorption/emission.