Results of molecular dynamics simulations on structural, vibrational and relaxational properties of zeolite ZSM-5 based amorphous solids are presented. The effects of extent of amorphization, measured by an energetic criterion, on properties like distribution of coordination numbers, internal surface area, ring statistics and effective pore size are studied. Ring statistics indicates that upon amorphization not only rings with larger size break down to give rings with smaller size, but that for intermediate degree of amorphization also larger rings are generated. The vibrational density of states was determined for different extents of amorphization. The vibrational modes are analyzed by projecting them on those of the SiO4 and Si-O-Si subunits and individual frequency-dependent contributions of stretching, bending and rotation are discussed. Analysis of low-frequency spectrum show that for higher crystallinity the intensity of the boson peak decreases upon amorphization, whereas the opposite behavior is observed for forms with lower crystallinity. These effects are explained in the framework of Maxwell counting of floppy modes. The modes associated with the boson peak for these materials are found to be mainly optic in nature. Relaxations were studied for temperatures below the critical temperature. At low temperatures the relaxations comprise mainly one-dimensional chains of atoms. The dimensionality of the relaxing centers increases with the temperature due to side branching. The possibility of having reversible jumps decreases with increasing temperature due to a strong drop in the potential energy during aging. There exist very prominent peaks in the van Hove correlation functions as a manifestation of the hopping processes. The dynamics of the oxygen atoms is found to be more heterogeneous than those of the silicon atoms. Ab initio many-body calculations on the strain energy ofW-silica, taken as a model system for edge-sharing tetrahedral SiO2-systems with respect to corner-sharing ones as in a-quartz was performed. Correlation contributions are found to play an important role to determine the stability of edge-sharing units. Our calculation reveal that edge-sharing SiO4 tetrahedra in (partially) amorphous silicate systems are possible at a modest energetic expense
