Influence of hydrogen on mechanical and thermodynamic properties of α-Nb₅Si₃ from first-principles calculations

ABSTRACT

The hydrogen embrittlement plays a crucial role in high-temperature material. However, the hydrogen embrittlement mechanism of Nb₅Si₃ is entirely unclear. To solve the key problem, we use the first-principles calculations to study the H-doped mechanism and influence of hydrogen on the elastic properties, brittle-or-ductile behaviour and Debye temperature of α-Nb₅Si₃. According to the structural feature, we consider four H-doped sites. We find that hydrogen prefers to occupy the H_-ST(4) site because of the strong localised hybridisation between hydrogen and α-Nb₅Si₃. Importantly, H-doping weakens the volume deformation resistance, shear deformation resistance and elastic stiffness of α-Nb₅Si₃. In particular, hydrogen results in hydrogen embrittlement of α-Nb₅Si₃ due to the formation of Si-H bond and Nb-H bond. In addition, the calculated Debye temperature of H_-ST(1) site and H_-ST(3) site is larger than that of α-Nb₅Si₃.

KEYWORDS:

• Brittleness
• ceramics
• first-principles calculations
• high-temperature materials
• transition metals
• mechanical properties

Acknowledgements

We also thank Lady Yun Zheng and Runxi Pan for help.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work is supported by National Natural Science Foundation of China [grant number 51274170] and the State Key Laboratory of Advanced Technology for Comprehensive Utilization of Platinum Metals [grant number SKL-SPM-201816].