AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
First-Principles Molecular Dynamics Simulation of Sulfuric Acid - Ammonia/Dimethylamine Clusters
VILLE LOUKONEN, I-Feng William Kuo, Matt J. McGrath, Hanna Vehkamäki, University of Helsinki
Abstract Number: 79 Working Group: Aerosol Nucleation: From Clusters to Nanoparticles
Abstract Today, the modern aerosol particle measurement devices are continuously reaching smaller and smaller diameter sizes: they routinely see small molecular clusters, and, some can even reach down to individual molecules. Regardless of this rapid development, currently the only direct way to probe the very first steps of aerosol particle formation are various computational techniques based on quantum mechanics. Here, we present results from first-principles molecular dynamics simulations investigating the stability of small (sulfuric acid)$_n (ammonia)$_(n-1) and (sulfuric acid)$_n (dimethylamine)$_n clusters (n=2,3,4). When these gases are present in the atmosphere, the studied pre-nucleation embryos are likely to form and the dynamics of these clusters will in part determine the dynamics of particle formation.
In these simulations the thermal motion of the molecules was taken explicitly into account. We found that the stability of the clusters is dependent on the hydrogen bonding patterns the molecules are able to form. Also, even after an equilibrium bonding pattern had emerged, the clusters showed pronounced bond rearrangement: the bonding patterns stayed the same, but the individual atoms forming the bonds changed, i.e. the thermal energy kept the molecules rotating. Regardless of this behaviour, the clusters remained bound together.