Structure and properties of silica nanoclusters at high temperatures

The properties of silica clusters at temperatures from 1500 to 2800 K are investigated using classical molecular dynamics simulations for particles containing up to 1152 atoms. We found that atoms in the cluster were arranged in a shell-like structure at low temperatures, and that the radial density profile peaked near the outer edge of the particle. Smaller clusters have much higher pressures, with the magnitudes corresponding quite well to those obtained from the Laplace--Young equation, when evaluated in a self-consistent manner using our derived surface tension. Our computed surface tension did not show any significant size-dependent behavior in contrast to the decreasing surface tension observed for Lennard--Jones liquid clusters. Finally our computed diffusion coefficients in the liquid state are seen to be larger than bulk computed diffusivities. A discussion regarding the relevance of these computations on the growth of silica nanoparticles is presented.