Spontaneous Self-Assembly of Silica Nanocages into Inorganic Framework Materials

The possibility of the formation of different silica nanostructures based on fully coordinated spheroidal nanocages (SiO2)24 is theoretically investigated using a pairwise potential and the ReaxFFSiO reactive force field. Molecular dynamics simulations at T = 300 K predict that while these nanocages are thermally stable, they spontaneously undergo dimerization upon contact by forming two siloxane bridges. The corresponding reaction pathways obtained with both methods are quantitatively confirmed by electronic structure calculations performed at the Hartree-Fock and density functional theory levels. The barrierless dimerization of silica nanocages is the first step of subsequent polymerizations into strongly bound inorganic materials. Routes to polymerization and possible applications are discussed.