Strain effects on monolayer MoSi2N4: ideal strength and failure mechanism

TL;DR

This study uses first-principles calculations to explore the mechanical properties, ideal strength, and failure mechanisms of monolayer MoSi2N4, revealing its high tensile strength and unique failure behaviors compared to similar materials.

Contribution

It provides the first detailed computational analysis of MoSi2N4's mechanical properties, including tensile strengths and failure mechanisms, highlighting its superior strength over MoS2.

Findings

Monolayer MoSi2N4 withstands stresses up to 51.6 GPa (zigzag) and 49.2 GPa (armchair).

Critical strains are 26.5% (zigzag) and 17.5% (armchair).

Higher elastic moduli and tensile strengths than MoS2.

Abstract

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.