Structural characterization of cubic silicon nitride

Structural characterization of the third polymorph of silicon nitride, synthesized under high-pressure and high-temperature conditions, has been obtained by Rietveld structure refinements of X-ray powder diffraction data recorded using synchrotron radiation. The material has a cubic spinel structure at 295 K with a space group Fd-3m, Z=8, a unit cell of $a=7.7339 \pm 0.0001\un{\mbox{\AA}}$, nitrogen position $x=0.2583 \pm 0.0001$, and density $\rho=3.75 \pm 0.02\un{g\, cm^{-3}}$. The complete structural data obtained should offer a firm basis for understanding the properties of the novel material. One example is present for the Raman spectroscopy data of the material.