Recent synthesis of platinum nitride has provoked considerable interest on account of the compound's anomalously high bulk modulus, which was more than 30% higher than that of the parent metal. Numerous theoretical studies had since offered contradicting hypotheses on the structure and properties of this compound. Here it was shown, based on first-principles calculations, that the recently synthesized phase of platinum nitride has the pyrite structure. In the PtN2 pyrite structure single-bonded N2 units occupy the octahedral interstitial sites of the Pt close-packed lattice, giving rise to strong, directional Pt-N bonds and to an insulating character. Excellent agreement with X-ray, Raman, and compressibility measurements was obtained.

Interstitial Di-Nitrogen Makes PtN2 an Insulating Hard Solid. A.F.Young, J.A.Montoya, C.Sanloup, M.Lazzeri, E.Gregoryanz, S.Scandolo: Physical Review B, 2006, 73[15], 153102 (4pp)