Stress-Strain Relations and Deformation Mechanisms of ZrN and HfN Superconductors

Zirconium and hafnium nitrides are charmingly hard superconductors [X. J. Chen et al. Proc. Natl. Acad. Sci. U.S.A., 2005, 102, 3198] with specific application under extreme conditions. Understanding the intrinsic hardness, especially under Vickers indentation deformation, in these superconductors is very important. Here, we perform first-principles studies of the stress-strain relations and deformation mechanisms of ZrN and HfN under compressive, tensile, pure shear, and indentation strains. The results offer a comprehensive description of their versatile stress responses, and the calculated indentation shear strengths for ZrN and HfN agree well with experimental results. The superior performance characteristics of HfN, compared to the isostructural ZrN, is attributed to the higher valence electron concentration that strengthens the Hf-N bonds. These results reveal the atomistic mechanisms for the mechanical properties of ZrN and HfN, providing insights for further exploration of hard and ultrahard transition-metal compounds.

Automated summary

This study investigates the stress-strain relations and deformation mechanisms of ZrN and HfN under different strains using first-principles calculations. The results provide a comprehensive description of their versatile stress responses and confirm the calculated indentation shear strengths. Additionally, it is found that HfN exhibits superior mechanical properties compared to ZrN, which is attributed to its higher valence electron concentration.