CLOSE PACKING AND PRESSURE-INDUCED AMORPHIZATION

Recently a large number of crystalline compounds have been discovered to amorphize at high pressures. However, the molecular origin of this transformation is not understood. In this article, we show that this is a consequence of a competition between the close-packing and long range order-a principle well known in organic crystallography. We show that the tendency of these systems to acquire higher coordination under compression is sterically hindered at some pressure due to the strong nature of inter-molecular bonding of building Mocks. This hindrance drives the system to sacrifice the translational order to achieve better packing. The application of principle is shown through the examples of Ca(OH)2, SiO2, ke, LiKSO4, etc.