TY - JOUR
T1 - Hydration of Atmospheric Molecular Clusters II
T2 - Organic Acid–Water Clusters
AU - Kildgaard, Jens Vive
AU - Mikkelsen, Kurt Valentin
AU - Bilde, Merete
AU - Elm, Jonas
PY - 2018/11/1
Y1 - 2018/11/1
N2 - Using computational methods, we study the gas phase hydration of three different atmospherically relevant organic acids with up to 10 water molecules. We study a dicarboxylic acid (pinic acid) and a tricarboxylic acid (3-methyl-1,2,3-butanetricarboxylic acid (mbtca)) that are both identified as products from α-pinene oxidation reactions. We also study a 2-oxohexanediperoxy acid (ohdpa) that has been identified as a product from cyclohexene autoxidation. To sample the cluster structures, we employ our recently developed systematic hydrate sampling technique and identify a total of 551 hydrate clusters. The cluster structures and thermochemical parameters (at 298.15 K and 1 atm) are obtained at the ωB97X-D/6-31++G(d,p) level of theory, and the single point energy of the clusters have been refined using a high level DLPNO-CCSD(T)/aug-cc-pVTZ calculation. We find that all three tested organic acids interact significantly more weakly with water compared to the primary nucleation precursor sulfuric acid. Even at 100% relative humidity (298.15 K and 1 atm), we find that ohdpa remains unhydrated and only the monohydrate of pinic acid and mbtca are slightly populated (4% and 2%, respectively). From the obtained molecular structures, potential implications for the ice nucleating ability of aerosol particles is discussed.
AB - Using computational methods, we study the gas phase hydration of three different atmospherically relevant organic acids with up to 10 water molecules. We study a dicarboxylic acid (pinic acid) and a tricarboxylic acid (3-methyl-1,2,3-butanetricarboxylic acid (mbtca)) that are both identified as products from α-pinene oxidation reactions. We also study a 2-oxohexanediperoxy acid (ohdpa) that has been identified as a product from cyclohexene autoxidation. To sample the cluster structures, we employ our recently developed systematic hydrate sampling technique and identify a total of 551 hydrate clusters. The cluster structures and thermochemical parameters (at 298.15 K and 1 atm) are obtained at the ωB97X-D/6-31++G(d,p) level of theory, and the single point energy of the clusters have been refined using a high level DLPNO-CCSD(T)/aug-cc-pVTZ calculation. We find that all three tested organic acids interact significantly more weakly with water compared to the primary nucleation precursor sulfuric acid. Even at 100% relative humidity (298.15 K and 1 atm), we find that ohdpa remains unhydrated and only the monohydrate of pinic acid and mbtca are slightly populated (4% and 2%, respectively). From the obtained molecular structures, potential implications for the ice nucleating ability of aerosol particles is discussed.
U2 - 10.1021/acs.jpca.8b07713
DO - 10.1021/acs.jpca.8b07713
M3 - Journal article
C2 - 30351100
SN - 1089-5639
VL - 122
SP - 8549
EP - 8556
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
IS - 43
ER -