Hydration of Atmospheric Molecular Clusters III : Procedure for Efficient Free Energy Surface Exploration of Large Hydrated Clusters

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Rasmussen , F R , Kubecka , J , Besel , V , Vehkamäki , H , Mikkelsen , K V , Bilde , M & Elm , J 2020 , ' Hydration of Atmospheric Molecular Clusters III : Procedure for Efficient Free Energy Surface Exploration of Large Hydrated Clusters ' , Journal of Physical Chemistry A , vol. 124 , no. 25 , pp. 5253-5261 . https://doi.org/10.1021/acs.jpca.0c02932

Title: Hydration of Atmospheric Molecular Clusters III : Procedure for Efficient Free Energy Surface Exploration of Large Hydrated Clusters
Author: Rasmussen, Freja Rydahl; Kubecka, Jakub; Besel, Vitus; Vehkamäki, Hanna; Mikkelsen, Kurt V.; Bilde, Merete; Elm, Jonas
Contributor organization: INAR Physics
Institute for Atmospheric and Earth System Research (INAR)
University Management
Date: 2020-06-25
Language: eng
Number of pages: 9
Belongs to series: Journal of Physical Chemistry A
ISSN: 1089-5639
DOI: https://doi.org/10.1021/acs.jpca.0c02932
URI: http://hdl.handle.net/10138/330315
Abstract: Sampling the shallow free energy surface of hydrated atmospheric molecular clusters is a significant challenge. Using computational methods, we present an efficient approach to obtain minimum free energy structures for large hydrated clusters of atmospheric relevance. We study clusters consisting of two to four sulfuric acid (sa) molecules and hydrate them with up to five water (w) molecules. The structures of the "dry" clusters are obtained using the ABCluster program to yield a large pool of low-lying conformer minima with respect to free energy. The conformers (up to ten) lowest in free energy are then hydrated using our recently developed systematic hydrate sampling technique. Using this approach, we identify a total of 1145 unique (sa)(2-4)(w)(1-5) cluster structures. The cluster geometries and thermochemical parameters are calculated at the omega B97X-D/6-31++G(d,p) level of theory, at 298.15 K and 1 atm. The single-point energy of the most stable clusters is calculated using a high-level DLPNO-CCSD(T-0)/aug-cc-pVTZ method. Using the thermochemical data, we calculate the equilibrium hydrate distribution of the clusters under atmospheric conditions and find that the larger (sa)(3) and (sa)(4) clusters are significantly more hydrated than the smaller (sa)(2) cluster or the sulfuric acid (sa)(1) molecule. These findings indicate that more than five water molecules might be required to fully saturate the sulfuric acid clusters with water under atmospheric conditions. The presented methodology gives modelers a tool to take the effect of water explicitly into account in atmospheric particle formation models based on quantum chemistry.
Subject: 114 Physical sciences
AB-INITIO
AMINES
BINDING-ENERGIES
DIMETHYLAMINE
NUCLEATION
PARTICLE FORMATION
STABILITY
SULFURIC-ACID DIMERS
THERMOCHEMISTRY
WATER CLUSTERS
Peer reviewed: Yes
Rights: unspecified
Usage restriction: openAccess
Self-archived version: acceptedVersion


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