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.