title: Osmium diboride, an ultra-incompressible, hard material.
abstract: The need for wear- and scratch-resistant materials drives the quest for new superhard materials. In this work, we apply two design parameters to identify ultra-incompressible, superhard materials-high valence electron density and high bond covalency. Our first example of such a material is OsB2. The bulk modulus of OsB2 was measured using in situ high-pressure X-ray diffraction and was determined to be in the range of 365-395 GPa. While this value is slightly less than that of the bulk modulus of diamond, due to the anisotropic crystal structure of OsB2, the axis compressibility in the orthorhombic c-direction is less than the axis compressibility found in diamond. OsB2 also scratches the surface of a sapphire window, indicating that the hardness of OsB2 exceeds 2000 kg/mm2.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Los Angeles, 90095-1569, USA.
authors.forename: Robert W
authors.initials: RW
authors.lastname: Cumberland
authors.forename: Michelle B
authors.initials: MB
authors.lastname: Weinberger
authors.forename: John J
authors.initials: JJ
authors.lastname: Gilman
authors.forename: Simon M
authors.initials: SM
authors.lastname: Clark
authors.forename: Sarah H
authors.initials: SH
authors.lastname: Tolbert
authors.forename: Richard B
authors.initials: RB
authors.lastname: Kaner