Change of free energy in heteromolecular nucleation: Electrostatic energy contribution

Abstract

The presence of foreign particles in vapor is known to promote the formation of clusters and phase transition at lower supersaturation. Our primary object here is to assess the contribution of the electrostatic energy to the total free energy change owing to the presence of a charged or uncharged foreign particle (atom or molecule) during the formation of heteromolecular clusters. Unlike the Thomson’s ’’electrothermodynamic’’ theory, we introduce the contribution of the higher electric moment (dipole) and polarization of the foreign particle, in addition to its monopole charge contribution. The present theory predicts: (1) there is no strong charge sign preference in the promotion of nucleation, (2) the size (’’radius’’) differences of ions or neutral foreign particles largely determine differences in the free energy change and thus in the promotion of nucleation, and (3) the differences in the dipole moments and polarizabilities of the charged or uncharged foreign particles are also important for such distinctions, particularly in the case of the foreign particles of nearly the same size. In the limiting case of zero polarizability and zero dipole moment associated with an ion, our present theory recovers exactly the same functional dependency on the charge, ionic radius, and the cluster size as in the electrothermodynamic theory of Thomson. .