Recently, two-dimensional monolayer MoSi₂N₄ with hexagonal structure was successfully synthesized in experiment (Hong et al. 2020 Science 369, 670). The fabricated monolayer MoSi₂N₄ is predicted to have excellent mechanical properties. Motived by the experiment, we perform first-principles calculations to investigate the mechanical properties of monolayer MoSi₂N₄, including its ideal tensile strengths, critical strains, and failure mechanisms. Our results demonstrate that monolayer MoSi₂N₄ can withstand stresses up to 51.6 and 49.2 GPa along zigzag and armchair directions, respectively. The corresponding critical strains are 26.5% and 17.5%, respectively. For biaxial strain, the ideal tensile strength is 50.6 GPa with a critical strain of 19.5%. Compared with monolayer MoS₂, monolayer MoSi₂N₄ possesses much higher elastic moduli and ideal tensile strengths for both uniaxial and biaxial strains. Interestingly, the critical strain and failure mechanism of zigzag direction in MoSi₂N₄ are almost the same as those of armchair direction in MoS₂, while the critical strain and failure mechanism of armchair direction for MoSi₂N₄ are similar to the ones of zigzag direction for MoS₂. Our work reveals the remarkable mechanical characteristics of monolayer MoSi₂N₄.

最近，在实验中成功地合成了具有六边形结构的二维单层MoSi ₂ N ₄（Hong等人，2020 Science 369，670）。预测所制造的单层MoSi ₂ N ₄具有优异的机械性能。基于实验的动机，我们执行第一性原理计算以研究单层MoSi ₂ N ₄的机械性能，包括其理想的拉伸强度，临界应变和破坏机理。我们的结果表明，单层MoSi ₂ N ₄可以沿之字形和扶手椅方向分别承受高达51.6 GPa和49.2 GPa的应力。相应的临界应变分别为26.5％和17.5％。对于双轴应变，理想的抗拉强度为50.6 GPa，临界应变为19.5％。与单层MoS ₂相比，单层MoSi ₂ N ₄具有更高的弹性模量和单轴和双轴应变的理想拉伸强度。有趣的是，MoSi ₂ N ₄中之字形方向的临界应变和破坏机制与MoS ₂中扶手椅方向的临界应变和破坏机制几乎相同，而MoSi ₂ N ₄的扶手椅方向的临界应变和破坏机制是相同的。与MoS ₂的之字形方向相似。我们的工作揭示了MoSi ₂ N ₄单层的显着机械特性。