Synthesis of Novel Transition Metal NitridesIrN2andOsN2

Abstract

Two new transition metal nitrides, ${\mathrm{IrN}}_2$ and ${\mathrm{OsN}}_2$, were synthesized at high pressures and temperatures using laser-heated diamond-anvil cell techniques. Synchrotron x-ray diffraction was used to determine the structures of novel nitrides and the equations of states of both the parent metals as well as the newly synthesized materials. The compounds have bulk moduli comparable with those of the traditional superhard materials. For ${\mathrm{IrN}}_2$, the measured bulk modulus [$K_0=428(12)\mathrm{GPa}$] is second only to that of diamond ($K_0=440\mathrm{GPa}$). Ab initio calculations indicate that both compounds have a metal:nitrogen stoichiometry of $1:2$ and that nitrogen intercalates in the lattice of the parent metal in the form of single-bonded N-N units.