Carbon-rich superhard ruthenium carbides from first-principles

Publication date: 5 March 2017
Source:Materials & Design, Volume 117
Author(s): Shipeng Zhao, Yali Yang, Jian Lu, Wei Wu, Sheng Sun, Xi Li, Xinluo Zhao, Shixun Cao, Jincang Zhang, Wei Ren
Compounds formed by transition metals and light elements have attracted increasing attention owing to superior functionalities. Here, high throughput first-principles calculations are employed to investigate the crystal structures and physical properties of ruthenium carbides with various stoichiometries. It is found that the R3¯m-Ru2C, R3¯m-RuC, P3¯m1-Ru2C3, P3¯m1-RuC2, P3¯m1-RuC3 and C2/c-RuC4 are the ground states for the respective chemical compositions at ambient pressure, from a systematical investigation of both thermodynamic and mechanical stabilities, as well as phonon dispersions. Further calculations indicate that P3¯m1-RuC3 and P63/mmc-RuC4 are ultra-incompressible with high bulk and shear modulus. Subsequent empirical calculations predict that the carbon-rich P3¯m1-RuC3 and P63/mmc-RuC4 are superhard materials with a large Vickers hardness of 45.1GPa and 41.5GPa, respectively. In addition, a strong covalent CC bonding was observed from the electronic localization function contours of all the ground states, which is crucial for their excellent mechanical properties.

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