Prediction of novel ultra-incompressibility compounds TM₂B (TM=Mo, W, Re and Os) by first-principles calculations

Abstract

Several novel ultra-incompressibility compounds TM₂B (TM = Mo, W, Re and Os) have been predicted by means of the first-principles calculations. Those novel compounds were assumed to have a ReB₂-type structure [P6₃/mmc space group (No.194, Z = 2), atomic sites: TM 4f (2/3, 1/3, z), B 2c (1/3, 2/3, 1/4)]. We calculated the mechanical properties of the TM₂B, and the results reveal that they exhibit brittle behaviour and mechanically stable. The hardness values are 23.8 GPa, 23.3 GPa, 26.6 GPa and 26.3 GPa for Mo₂B, W₂B, Re₂B and Os₂B, respectively, which suggests that they are hard materials. Additionally, we found that the anisotropy of Re₂B is weaker than the others. Finally, the Mo₂B has the highest Debye temperature (905.8 K), while Os₂B has the lowest Debye temperature (615.5 K). We hoped that our results can help to offer a theoretical data for future experimental work and application of TM₂B.

Keywords:

• First-principles calculations
• transition-metal semi-borides
• mechanical properties
• hardness
• thermodynamic properties

Acknowledgements

The authors thank the project of innovative talents of North China University of Water Resources and Electric Power (grant number 70483) and the programme for innovative research team (in science and technology) in University of Henan Province (Nos.16IRTSTHN017) for financial support.