Structural characterization of cubic silicon nitride

Structural characterization of the third polymorph of silicon nitride, synt hesized under high-pressure and high-temperature conditions, has been obtai ned by Rietveld structure refinements of X-ray powder diffraction data reco rded 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+/-0.00 01 Angstrom, nitrogen position x = 0.2583+/-0.0001, and density rho = 3.75/-0.02 g cm(-3) The complete structural data obtained should offer a firm b asis for understanding the properties of the novel material. One example is present for the Raman spectroscopy data of the material.