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Molecular Interaction of Pinic Acid with Sulfuric Acid: Exploring the Thermodynamic Landscape of Cluster Growth

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  • Jonas Elm, Kemisk Institut, Denmark
  • Theo Kurten, University of Helsinki, Finland
  • Merete Bilde
  • Kurt Valentin Mikkelsen, Kemisk Institut, Denmark
We investigate the molecular interactions between the semivolatile alpha-pinene oxidation product pinic acid and sulfuric acid using computational methods. The stepwise Gibbs free energies of formation have been calculated utilizing the M06-2X functional, and the stability of the clusters is evaluated from the corresponding Delta G values. The first two additions of sulfuric acid to pinic acid are found to be favorable with Delta G values of -9.06 and -10.41 kcal/mol. Addition of a third sulfuric acid molecule is less favorable and leads to a structural rearrangement forming a bridged sulfuric acid-pinic acid cluster. The involvement of more than one pinic acid molecule in a single cluster is observed to lead to the formation of favorable (pinic acid)(2)(H2SO4) and (pinic acid)(2)(H2SO4)(2) clusters. The identified most favorable growth paths starting from a single pinic acid molecule lead to closed structures without the further possibility for attachment of either sulfuric acid or pinic acid. This suggests that pinic acid cannot be a key species in the first steps in nucleation, but the favorable interactions between sulfuric acid and pinic acid imply that pinic acid can contribute to the subsequent growth of an existing nucleus by condensation.
Original languageEnglish
JournalJournal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory
Volume118
Issue36
Pages (from-to)7892-7900
Number of pages9
ISSN1089-5639
DOIs
Publication statusPublished - 11 Sep 2014

    Research areas

  • ATMOSPHERIC NUCLEATION PRECURSORS, DENSITY-FUNCTIONAL THEORY, PARTICLE FORMATION, AEROSOL NUCLEATION, ORGANIC-AEROSOL, NANOAEROSOL CLUSTERS, DYNAMICS SIMULATIONS, ALPHA-PINENE, OZONOLYSIS, ENERGIES

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