Osmium diboride, an ultra-incompressible, hard material

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 materialshigh 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.