Nitride Spinel: An Ultraincompressible High‐Pressure Form of BeP 2 N 4

Owing to its outstanding elastic properties, the nitride spinel γ‐Si 3 N 4 is of considered interest for materials scientists and chemists. DFT calculations suggest that Si 3 N 4 ‐analog beryllium phosphorus nitride BeP 2 N 4 adopts the spinel structure at elevated pressures as well and shows outstanding elastic properties. Herein, we investigate phenakite‐type BeP 2 N 4 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 BeP 2 N 4 was refined from pressure‐dependent in situ synchrotron powder X‐ray diffraction measurements down to ambient pressure, which proves spinel‐type BeP 2 N 4 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 BeP 2 N 4 is an ultraincompressible material.