Faculty of Natural Sciences

TY - JOUR

T1 - Molecular Interaction of Pinic Acid with Sulfuric Acid

T2 - Exploring the Thermodynamic Landscape of Cluster Growth

AU - Elm, Jonas

AU - Kurten, Theo

AU - Bilde, Merete

AU - Mikkelsen, Kurt Valentin

PY - 2014/9/11

Y1 - 2014/9/11

N2 - 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.

AB - 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.

KW - ATMOSPHERIC NUCLEATION PRECURSORS

KW - DENSITY-FUNCTIONAL THEORY

KW - PARTICLE FORMATION

KW - AEROSOL NUCLEATION

KW - ORGANIC-AEROSOL

KW - NANOAEROSOL CLUSTERS

KW - DYNAMICS SIMULATIONS

KW - ALPHA-PINENE

KW - OZONOLYSIS

KW - ENERGIES

U2 - 10.1021/jp503736s

DO - 10.1021/jp503736s

M3 - Journal article

C2 - 24988284

VL - 118

SP - 7892

EP - 7900

JO - Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory

JF - Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory

SN - 1089-5639

IS - 36

ER -