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Is osmium diboride an ultra-hard material?
Jun Yang1, Hong Sun, Changfeng Chen
1Department of Physics, Shanghai Jiao Tong University, Shanghai 200240, China.
Journal of the American Chemical Society
|May 16, 2008
Summary
First-principles calculations reveal OsB2 exhibits anisotropic shear strength. Its high resistance to (001)[100] shear contributes to its ultra-hard nature, but weak (001)[010] shear limits some applications.
Area of Science:
- Materials Science
- Computational Materials Science
- Solid State Physics
Background:
- Osmium diboride (OsB2) represents a new class of ultra-hard materials.
- These materials combine light, covalent elements with heavy transition metals.
- Understanding deformation mechanisms is crucial for designing novel hard materials.
Purpose of the Study:
- To investigate the ideal tensile and shear strength of orthorhombic OsB2.
- To elucidate the atomistic deformation modes governing its mechanical properties.
- To correlate calculated strengths with experimental hardness observations.
Main Methods:
- First-principles calculations were employed to simulate mechanical behavior.
- Tensile and shear strength calculations were performed on the orthorhombic OsB2 structure.
- Anisotropy in shear strength was analyzed across different crystallographic directions.
Main Results:
- Orthorhombic OsB2 exhibits highly anisotropic shear strength on the (001) plane.
- Peak shear stress was significantly higher in the (001)[100] direction (26.9 GPa) compared to the (001)[010] direction (9.1 GPa).
- Calculated strengths align with experimental Vickers hardness of 30 GPa on the (001) plane.
Conclusions:
- The strong resistance to (001)[100] shear deformation is responsible for OsB2's high Vickers hardness.
- The weaker (001)[010] shear strength limits its use in abrasive and cutting applications.
- Understanding anisotropic deformation modes is vital for the rational design of advanced ultra-hard materials.
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