Nitride Spinel: An Ultraincompressible High-Pressure Form of BeP2N4

Owing to its outstanding elastic properties, the nitride spinel gamma-Si3N4 is of considered interest for materials scientists and chemists. DFT calculations suggest that Si3N4-analog beryllium phosphorus nitride BeP2N4 adopts the spinel structure at elevated pressures as well and shows outstanding elastic properties. Herein, we investigate phenakite-type BeP2N4 by single-crystal synchrotron X-ray diffraction and report the phase transition into the spinel-type phase at 47 GPa and 1800 K in a laser-heated diamond anvil cell. The structure of spinel-type BeP2N4 was refined from pressure-dependent in situ synchrotron powder X-ray diffraction measurements down to ambient pressure, which proves spinel-type BeP2N4 a quenchable and metastable phase at ambient conditions. Its isothermal bulk modulus was determined to 325(8) GPa from equation of state, which indicates that spinel-type BeP2N4 is an ultraincompressible material.