COMPUTATIONAL MODELING OF AMORPHOUS SILICA .3. MODELING THE INITIAL STRUCTURES - SILICA-GEL

A qualitative algorithm for construction of large clusters of silica gel model structures is used. According to this algorithm and in line with our classification of dispersive silicas, silica gel is regarded as cyclosilica, which is characterized by loose packing of the cycles of silicon-oxygen tetrahedra. A model of silica gel structure is proposed where the primary structural fragments are hollow frameworks with a network surface. The units of the surface network are formed by nonplanar [SiO4] chain cycles of various sizes. This structural model makes if possible to explain the peculiarities of the vibration spectra of the framework, hydroxyl, and aqueous components of silica gels.