Reactive Modeling of Silica Synthesis*

Reactive Molecular Dynamics can describe complex problems where quantum approaches are too slow and do not properly take into account environmental effects and on the other hand classical molecular dynamics is not capable of describing reactions. ReaxFF is a good moxdel for such systems but it needs to be properly trained for the system at hand. In this study we train a ReaxFF model for silica synthesis as an industrially important question is to characterize silica gels and organo-silicon surface coatings. These are formed by reactive condensation of organo-silicon precursors. The morphologies of silica gels obtained from alkoxysilanes can then be determined using our newly trained models and improved simulation techniques. It is found that the gels obtained from trialkoxysilanes are more loosely bonded, and that the chemistry of the headgroup is important to the gel morphology. We furthermore can describe the chemisorption of alkoxysilanes with organic headgroups to hydroxylated silica surfaces. This approach can also be applied to zeolite synthesis.