High pressure behaviour of the -cristobalite-type phase of phosphorus oxynitride, PON

Phosphorus oxynitride, PON, is isoelectronic with and can be used as a model for silica. The crystalline behaviour of the -cristobalite-type phase was determined as a function of pressure by angular dispersive x-ray diffraction in a diamond anvil cell to 48 GPa. No evidence for a phase transition or amorphization was observed. The cell parameters were measured as a function of pressure. The macroscopic bulk modulus is 71(3) GPa with a first pressure derivative of 3.2(5). The polyhedral bulk modulus was inferred to be about 800 GPa, assuming that the tetrahedra remain regular.