Exploring superlubricity in multi-atomic layer 2D materials: MoSi₂N₄/MoSi₂N₄ homojunction and graphene/MoSi₂N₄ heterojunction

MoSi₂N₄, a newly synthesized two-dimensional material with seven atomic layers and no known three-dimensional parent crystal, shows excellent mechanical properties like high tensile strength, large elastic modulus, and superior thermal conductivity, making it a strong candidate for solid lubricants. Here, we systematically studied interfacial friction at MoSi₂N₄/MoSi₂N₄ homojunction and graphene/MoSi₂N₄ heterojunction via high-throughput first-principles calculations. Our findings show that the sliding potential barrier at the interface of graphene/MoSi₂N₄ heterojunction is markedly lower than that of the MoSi₂N₄/MoSi₂N₄ homojunction. The heterojunction also achieves superlubricity under normal loads from 0.8 to 4.8 nN (in 0.8 nN steps), with an ultralow friction coefficient (0.00034–0.000576) far below 0.001. Moreover, the average interfacial friction force in the MoSi₂N₄/MoSi₂N₄ homojunction decreases gradually as biaxial tensile strain rises from 0 to 8%, a phenomenon attributed to changes in the charge density difference. These findings confirm that MoSi₂N₄ is a highly promising multi-atomic layer solid lubricant with potential applications in nanoscale tribology.