Carbon-rich superhard ruthenium carbides from first-principles

• Published in: Materials & design 2017-03, Vol.117, p.353-362
• Main Authors: Zhao, Shipeng, Yang, Yali, Lu, Jian, Wu, Wei, Sun, Sheng, Li, Xi, Zhao, Xinluo, Cao, Shixun, Zhang, Jincang, Ren, Wei
• Format: Article
• Language: English
• Subjects: Dynamical stabilities; First-principles calculations; Mechanical properties
• ISSN: 0264-1275; 1873-4197
• DOI: 10.1016/j.matdes.2016.12.094

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. [Display omitted] •Ruthenium carbides with various stoichiometries were studied by density functional theory calculations.•Ground states of Ru2C, RuC, Ru2C3, RuC2, RuC3 and RuC4 are found, pressure-induced phase transitions are uncovered.•Two carbon-rich structures are found to have large Vickers hardness 45.1 GPa and 41.5 GPa.