QUANTUM-CHEMISTRY OF SOL-GEL SILICA CLUSTERS

Quantum calculations of rings and chains containing up to six hydrolized silica tetrahedra have been made using intermediate neglect of differential overlap (INDO) molecular orbital theory. Differences in molecular energies between rings and chains appears to be responsible for limiting the growth of particles in the sol prior to gelation. Changes in the structure and molecular energies of a 4-membered silicon ring with adsorption and desorption of H2O indicates a possible mechanism for the observed dilotometric behavior of porous Type VI sol-gel silica. © 1990.