MXenes are two‐dimensional carbides and nitrides with the formula of M n +1 X n and have attracted increasing interest in diverse fields. In this study, the structural, electronic, and mechanical properties of M 2 X (M = Zr, Hf; X = C, N) have been studied by using the first principles method. The ideal strain–stress curves in response to the tensile strain under uniaxial and biaxial tension have been evaluated. The results indicated that all the studied structures are metallic and stable both mechanically and dynamically. The hybridization between Zr 4 d (Hf 5 d ) and N 2 p orbitals lies lower in energy than that between Zr 4 d (Hf 5 d ) and C 2 p orbitals. M 2 N is relatively stiffer than M 2 C due to the large Young's modulus and shear modulus, in which Hf 2 N has the best mechanical performance. This is also confirmed by the strain–stress curves, where Hf 2 N has the highest ideal strength (41.9 GPa) and extended critical strain (13%). In addition, the shear modulus and Young's modulus are also the largest for Hf 2 N. Therefore, the improved elastic properties and high critical strain make Hf 2 N suited for applications in such as flexible devices.
Bo et al. (Wed,) studied this question.