(544f) Sticking Efficiency of Silica Clusters By Molecular Dynamics

Collisions between small clusters take place in the early stages of particle formation playing a key role in environmental and industrial processes, like condensation and sintering. Such collisions lead to the formation of larger particles. However, the impinging clusters do not always stick with each other upon collision, especially if they are small. However, a sticking probability of unity is assumed typically, regardless of cluster size.

Here, molecular dynamics simulations are used to model the collision between two silica clusters consisting of 18 up to 333 atoms. The method is based on Yang et al. (2018) to obtain the sticking rate of silica clusters in the gas-phase. In these atomistic simulations, the detailed structure and surface roughness of the clusters are accounted for, contrary to the classic collision theory of hard spheres. Furthermore, criteria for successful cluster-cluster collisions are proposed based on the collision time. The effect of temperature, cluster size and orientation as well as atom velocity and collision angle on the sticking probability is investigated.

The above method predicts accurately the sticking probability and condensation rate coefficients that can be used to correct the collision frequency of agglomerates. 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 and soot formation models.

Yang, H., Goudeli, E., & Hogan Jr, C. J. (2018). J Chem Phys, 148, 164304.