A perfect tetrahedral model for glassy SiO2

Glassy SiO2, the prototype of a saturated tetrahedral amorphous network, represents not only about a $50 × 109 market but also a surprisingly convoluted and intriguing physics problem. Despite a century of diffraction experiments, as of today, there is no fully satisfying structural model for it. Here, we present a structural model for amorphous SiO2 that consists of fully connected tetrahedra, consistent with the diffraction data at the partial structure factor level, and has the correct atomic density. The structures of saturated tetrahedral glasses are identical except for the position in which the connecting atom is placed relative to the line connecting the centers of the tetrahedra. The zero pressure density of these systems collapses on a single line solely dependent on the intertetrahedral distance.