Tropospheric Bioaerosols of Southwestern Siberia: Their Concentrations and Variability, Distributions and Long-term Dynamics

Abstract

Quantum methods, which are developed to accurately predict the physical properties of small clusters, are applied to study the water nucleation phenomenon. The self-consistency corrected (SCC) theory of water homogeneous nucleation, which satisfies the law of mass action and avoids the mismatch in the cluster distribution for monomers, overpredicts the nucleation by several orders of magnitude. In this study, we show that the overprediction is likely due to the inadequate description of thermodynamic properties of small water cluster using capillarity approximation. The Density Functional Theory (DFT) methods – PBEPBE and PW91PW91, were used to calculate the thermodynamic properties of (H2O)n (n = 1–10). These data were then used in the kinetic water nucleation model to study the effect of thermochemistries of the first ten water clusters on the prediction of nucleation rate by SCC. A considerable difference between Gibbs free energy changes of the (H2O)n formation used in classical nucleation thoery (CNT) and results obtained using quantum methods has been illustrated. We also found that predicted nucleation rates by the SCC model can be improved when the model is constrained by the stepwise Gibbs free energy changes obtained by DFT methods. This study highlights the importance of properly treating the thermochemistry of small cluster formation and demonstrates the feasibility of employing thermodynamic properties of small clusters obtained using quantum methods instead of those derived based on traditional capillarity approximation.