Structure and mechanical properties of osmium carbide: First-principles calculations

Synthesized osmium carbide (OsC) was reported in tungsten carbide (WC) structure, inconsistent with recent theoretical finding that the WC-structured OsC does not satisfy the mechanical stability criteria. The first-principles calculations of osmium carbide for nine hypothetical structures indicate that OsC with FeSi structure, NiAs structure, and CoSn structure satisfy the mechanical stability criteria. Based on the simulated x-ray diffraction data of WC structure and NiAs structure, we consider that the experimentally synthesized OsC is of the NiAs structure rather than the WC structure. In addition, the Os-C bond in NiAs-structured OsC has metallic feature, responsible for low hardness. (C) 2008 American Institute of Physics.