Role of Ions in Heteromolecular Nucleation: Free Energy Change of Hydrated Ion Clusters

  1. David R. Schryer
  1. S. H. Suck,
  2. T. S. Chen,
  3. R. W. Emmons,
  4. D. E. Hagen and
  5. J. L. Kassner Jr.

Published Online: 21 MAR 2013

DOI: 10.1029/GM026p0028

Heterogeneous Atmospheric Chemistry

Heterogeneous Atmospheric Chemistry

How to Cite

Suck, S. H., Chen, T. S., Emmons, R. W., Hagen, D. E. and Kassner, J. L. (1982) Role of Ions in Heteromolecular Nucleation: Free Energy Change of Hydrated Ion Clusters, in Heterogeneous Atmospheric Chemistry (ed D. R. Schryer), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM026p0028

Author Information

  1. Department of Physics and Graduate Center for Cloud Physics Research, University of Missouri-Rolla, Rolla, Missouri 65401

Publication History

  1. Published Online: 21 MAR 2013
  2. Published Print: 1 JAN 1982

ISBN Information

Print ISBN: 9780875900513

Online ISBN: 9781118663813



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The presence of foreign particles (i.e., ions) in vapor is known to enhance nucleation. Recently, less-biased molecular dynamics calculations of hydrated ion clusters were made by other researchers to compare with the classical electrochemical theory of Thomson. Using a theory developed earlier, we present here the computed excess free energies of the hydrated ion (Cs+ and F) clusters of opposite sign. This theory yields good agreement with the numerical molecular dynamics method in the estimation of the excess free energy. However, Thomson's theory predicts much smaller (in absolute magnitude) excess free energies at all cluster sizes than both ours and theirs. In view of a good agreement with the curvature variation of the excess free energy obtained by the accurate molecular dynamics method, their theory is promising particularly due to its merit of simplicity and analyticity. Further, good agreement with the less-biased molecular dynamics method (which requires the knowledge of only interaction potentials) leads us to a seemingly obvious but important conclusion: the difference in the excess free energies between the two oppositely charged ion clusters is largely due to the difference in the electrostatic interaction energy between the ion and water molecules since both the volume and surface energy terms remained unchanged in our calculations.