AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
Latent Heat for Condensation and Coagulation During Nanocluster Growth
HUAN YANG, Yannis Drossinos, Christopher Hogan Jr., University of Minnesota
Abstract Number: 53 Working Group: Aerosol Physics
Abstract Modelling of the growth rate of nanoclusters via monomer-cluster condensation or cluster-cluster coagulation is of importance in all aerosol systems where particles form from vapor phase precursors. An interesting feature of condensational and coagulational growth is that after a collision and binding event the internal energy of a newly formed cluster is higher than it would be at thermal equilibrium, i.e. condensation and coagulation events release heat. Typically, growth rate models are constructed either neglecting heat release (isothermal models) or assuming that the amount of heat released is equivalent to the bulk Latent heat of evaporation. However, at the nanocluster scale, the heat released to a cluster is not necessarily equal to the bulk latent heat, and may depend non-monotonically on the number of atoms or monomers in the colliding clusters as well as the product cluster. In an effort to better understand heat release during cluster growth, we have developed a theory to calculate the heat release and latent heat for cluster growth as a function of the sizes (number of atoms or monomers) in the colliding clusters and the product cluster. We show that the latent heat, defined as the energy released to the surroundings because of a collision and binding event, and the internal energy increase associated with the binding event, are not equivalent at the nanoscale. The calculation approach depends upon (1) conservation of the total energy during collision between two clusters (or monomer and cluster), and (2) internal equilibration of the newly formed cluster in an NVE environment. We will present the derivation of the new theoretical expression and a case study using Molecular Dynamics simulations with a many-body, non-local Embedded-Atom Method potential for gold cluster growth.