Computer modeling of nanoscale silica particles

Using the AM1 semi-empirical method and the geometry optimization procedure we study atomic and electronic structures of nanoscale silica particles containing up to 192 atoms. Two-fold Si-O rings were found to dominate in nanoparticles in contrast to bulk silica. The number of n-fold rings with n > 2 increases with the size of particles. Bond length and bond angle distributions were calculated. The shortest S-O, O-O and Si-Si interatomic distances are near 1.7 Angstrom, 3.0 Angstrom and 3.3 Angstrom, respectively. Average O-Si-O and Si-O-Si bond angles-are near 110 degrees and 130 degrees. Average electronic energy band gap is 6.9 eV.