| Abstract
| - Molecular dynamics simulations based on a reactive force field with charge transfer were used to model thesol−gel synthesis of nanoporous silica gels in an aqueous environment. Three distinct growth regimes emerge,depending on the solvent-to-silica ratio: compact nanoparticles, percolated silica networks, and branchedclusters. These growth regimes can be identified on the basis of distinctive structural features. In the case ofcompact particles, the radial distribution functions exhibit a broad maximum that coincides with the radius ofgyration of the aggregates, whereas in continuous networks the radial distribution function increases steadilybeyond the near-range structural features. Furthermore, these growth regimes can be distinguished on thebasis of the concentrations of structural defects, such as dangling bonds and residual OH groups. The growthkinetics of individual regimes are characterized by different relative contributions of atomic diffusion to theoverall aggregation rate. Finally, the resulting gel structures possess different mechanical stability, as can beassessed by quantifying the extents of structural collapse during simulated supercritical drying.
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