High-pressure crystal chemistry and amorphization of α-quartz

摘要: Single-crystal X-ray diffraction experiments on α-quartz at pressures to 15 GPa reveal structural instabilities that result in its gradual transition an amorphous state. With increasing pressure the average SiO distance (≈ 1.61 ± 0.01 A) and SiO4 tetrahedral volume 2.14 0.02 A3 remain constant. Compression of results from a dramatic decrease SiOSi angle corresponding inter-tetrahedral (i.e., OO) distances. The onset amorphization coincides with bending all angles less than 120° severe distortion tetrahedra, as oxygens approach close-packed configuration.