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Prediction of the Size Distributions of Methanol-Ethanol Clusters Detected in VUV Laser/Time-of-flight Mass Spectrometry

Liu, Yi and Consta, Styliani and Shi, Yujun and Lipson, R. H. and Goddard, William A., III (2009) Prediction of the Size Distributions of Methanol-Ethanol Clusters Detected in VUV Laser/Time-of-flight Mass Spectrometry. Journal of Physical Chemistry A, 113 (25). pp. 6865-6875. ISSN 1089-5639. https://resolver.caltech.edu/CaltechAUTHORS:20110719-145232702

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Abstract

The size distributions and geometries of vapor clusters equilibrated with methanol−ethanol (Me−Et) liquid mixtures were recently studied by vacuum ultraviolet (VUV) laser time-of-flight (TOF) mass spectrometry and density functional theory (DFT) calculations (Liu, Y.; Consta, S.; Ogeer, F.; Shi, Y. J.; Lipson, R. H. Can. J. Chem. 2007, 85, 843−852). On the basis of the mass spectra recorded, it was concluded that the formation of neutral tetramers is particularly prominent. Here we develop grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) frameworks to compute cluster size distributions in vapor mixtures that allow a direct comparison with experimental mass spectra. Using the all-atom optimized potential for liquid simulations (OPLS-AA) force field, we systematically examined the neutral cluster size distributions as functions of pressure and temperature. These neutral cluster distributions were then used to derive ionized cluster distributions to compare directly with the experiments. The simulations suggest that supersaturation at 12 to 16 times the equilibrium vapor pressure at 298 K or supercooling at temperature 240 to 260 K at the equilibrium vapor pressure can lead to the relatively abundant tetramer population observed in the experiments. Our simulations capture the most distinct features observed in the experimental TOF mass spectra: Et3H+ at m/z = 139 in the vapor corresponding to 10:90% Me−Et liquid mixture and Me3H+ at m/z = 97 in the vapors corresponding to 50:50% and 90:10% Me−Et liquid mixtures. The hybrid GCMC scheme developed in this work extends the capability of studying the size distributions of neat clusters to mixed species and provides a useful tool for studying environmentally important systems such as atmospheric aerosols.


Item Type:Article
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http://dx.doi.org/10.1021/jp900487xDOIArticle
http://pubs.acs.org/doi/full/10.1021/jp900487xPublisherArticle
ORCID:
AuthorORCID
Goddard, William A., III0000-0003-0097-5716
Additional Information:© 2009 American Chemical Society. Received: January 16, 2009; Revised Manuscript Received: May 08, 2009. Publication Date (Web): June 2, 2009. We acknowledge the financial support of the Natural Sciences and Engineering Research Council (NSERC) and Shared Hierarchical Academic Research Computing Network (SHARCNET) at UWO. S.C. is grateful for funding through a Premier’s Research Excellence Award. We also thank Faikah Ogeer for help on the MD simulations.
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Natural Sciences and Engineering Research Council (NSERC)UNSPECIFIED
Premier's Research Excellence AwardUNSPECIFIED
Issue or Number:25
Record Number:CaltechAUTHORS:20110719-145232702
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20110719-145232702
Official Citation:Prediction of the Size Distributions of Methanol−Ethanol Clusters Detected in VUV Laser/Time-of-Flight Mass Spectrometry Yi Liu, Styliani Consta, Yujun Shi, R. H. Lipson, William A. Goddard III The Journal of Physical Chemistry A 2009 113 (25), 6865-6875
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:24467
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:19 Jul 2011 22:52
Last Modified:03 Oct 2019 02:56

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