Recent synthesis of platinum nitride has provoked considerable interest on account of the compound's anomalously high bulk modulus, which is more than 30% higher than that of the parent metal. Numerous theoretical studies have since offered contradicting hypotheses on the structure and properties of this compound. Here we show, based on first-principles calculations, that the recently synthesized phase of platinum nitride has the pyrite structure. In the PtN2 pyrite structure single-bonded N-2 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 is obtained.
INFM, Democritos Natl Simulat Ctr, I-34014 Trieste, Italy; SISSA, Int Sch Adv Studies, I-34014 Trieste, Italy; Univ Paris 06, F-75252 Paris, France; Inst Phys Globe, F-75252 Paris 05, France; Inst Mineral & Phys Milieux Condenses, F-75252 Paris 05, France; Univ Edinburgh, Sch Phys, Edinburgh EH9 3JZ, Midlothian, Scotland; Univ Edinburgh, Ctr Sci Extreme Condit, Edinburgh EH9 3JZ, Midlothian, Scotland; Abdus Salam Int Ctr Theoret Phys, I-34014 Trieste, ItalyArticleEnglish