Molecular dynamics study of particle-particle collisions between hydrogen-passivated silicon nanoparticles

One of the significant challenges in the use of nanoparticles is the control of primary particle size and extent of agglomeration when grown from the gas phase. In this paper we evaluate a possible strategy of surface passivation. Here the particle-particle interaction of hydrogen-surface-terminated silicon nanoparticles has been evaluated using molecular dynamics simulation. Nanoparticles of the size between 200 and 6400 silicon atoms at 300-1800 K were studied with a reparametrized Kohen-Tully-Stillinger empirical interatomic potential. A hydrogen monolayer is shown to prevent coalescence between particles under thermal collision conditions. The critical approach energy for coalescence was found to increase with increasing particle size but decreases with increasing temperature. Both solid and liquid droplets were seen to bounce at thermal energies, and in some cases, "superelastic" collisions are observed, where the rebound kinetic energy of the droplet is higher than the approach energy. These results suggest that surface coatings can significantly retard nanoaerosol growth.