(527b) Binding Coefficients during Condensation of Au and Mg at High Temperatures By Molecular Dynamics Simulations

Collisions between molecules (or atoms) take place in the early stages of particle formation (nucleation), and play an important role in environmental and industrial processes, like condensation and chemical reactions. Such collisions lead to the formation of small clusters but the impinging molecules are not always captured successfully by the cluster, especially if they are small. However, a sticking probability of unity is assumed typically, regardless of cluster size.

Here, the sticking probability during homogeneous condensation of atoms (e.g. Au and Mg) on small clusters is calculated from first principles using Molecular Dynamics (MD) simulations accounting for the detailed cluster structure and surface roughness. The effect of temperature, cluster size and orientation as well as atom velocity and collision angle on the sticking probability is investigated. Criteria for successful atom-cluster collisions are proposed based on the collision time. The sticking efficiency, defined as the ratio of successful collisions over all possible collisions, decreases with decreasing particle size.

The above method predicts accurately the sticking probability and can be used to correct the collision kernel of clusters. The revised coagulation rates can be employed in greatly simplified population balance equation models coupled with fluid dynamics to facilitate the design and operation of aerosol reactors as well as in aerosol dynamics models.