AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Sulfuric Acid Hydration and Its Atmospheric Implications
BERHANE TEMELSO, George Shields, Bucknell University
Abstract Number: 768 Working Group: Aerosol Chemistry
Abstract The binary H$_2SO$_4-H$_2O nucleation is considered to be an important pathway for the formation of secondary aerosols in the atmosphere. We investigated the thermodynamics of sulfuric acid hydration using ab initio quantum mechanical methods. For H$_2SO$_4(H$_2O)$_n, (H$_2SO$_4)$_2(H$_2O)$_n, HSO$_4$^-(H$_2O)$_n and SO$_4$^(2-)(H$_2O)$_n where n = 1−6, we used a scheme combining molecular dynamics configurational sampling with high-level ab initio calculations to locate the global and many low lying local minima for each cluster size. From the Boltzmann averaged Gibbs free energies, we derived important conclusions about acid dissociation in small clusters, the stability of neutral and ionic species and the abundance of small sulfuric acid hydrates under atmospheric conditions. The extent of sulfuric acid hydration determined from our calculations is substantially different from predictions of simpler models and experiments. The implications of these findings on the discrepancy between experimental and theoretical nucleation rates as well as the different aerosol nucleation mechanisms is explored.