Hou Defeng, Niu Ziyu, Li Xuhong, Jing Xixiang, Sun Jing, Fan Xiaoli, Shi Junqin, Cao Tengfei
Research Center for Advanced Lubrication and Sealing Materials, School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an, Shaanxi 710072, P. R. China.
State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi'an, Shaanxi 710072, P. R. China.
Phys Chem Chem Phys. 2024 Jun 12;26(23):16792-16801. doi: 10.1039/d4cp01290a.
MN (M = Be, Mg, and Pt) represents a new class of van der Waals materials. These materials are characterized by exceptional electrical and thermal conductivities, remarkable intralayer mechanical strength, and weak interlayer interactions, making them prone to shearing and slipping. Therefore, MN has significant potential applications as a solid lubricant. However, until now, there have been only limited comprehensive theoretical investigations focusing on the frictional properties of MN systems. Here, the frictional performances of MN are systematically analyzed by applying first-principles high-throughput calculations. The results reveal that interlayer friction of MN decreases from MgN to BeN and then to PtN. The friction is directly determined by charge density variations during the sliding processes. The periodic formation and breaking of quasi-σ bonds in bilayer MgN leads to substantial variations in charge density and large interlayer friction. In contrast, the weak charge density alternations in PtN lead to rather low frictions in PtN. Moreover, surface functionalization effectively diminishes friction within bilayer MgN, but amplifies interlayer friction within bilayer PtN, and under surface functionalization interlayer friction can be efficiently modulated by out-of-plane polarizations. Interestingly, HBr-MgN exhibits two orders of magnitude lower COF compared to intrinsic bilayer MgN, leading to a phenomenon resembling superlubricity. These results significantly contribute to our understanding of the friction properties, offering valuable guidance for the practical implementation of MN in solid lubricants.
MN（M = 铍、镁和铂）代表了一类新型的范德华材料。这些材料的特点是具有出色的电导率和热导率、显著的层内机械强度以及较弱的层间相互作用，这使得它们易于剪切和滑动。因此，MN作为固体润滑剂具有重要的潜在应用。然而，到目前为止，针对MN体系摩擦性能的全面理论研究还很有限。在此，通过应用第一性原理高通量计算系统地分析了MN的摩擦性能。结果表明，MN的层间摩擦从MgN到BeN再到PtN逐渐降低。摩擦直接由滑动过程中的电荷密度变化决定。双层MgN中准σ键的周期性形成和断裂导致电荷密度的大幅变化和较大的层间摩擦。相比之下，PtN中较弱的电荷密度交替导致PtN中的摩擦较低。此外，表面功能化有效地降低了双层MgN中的摩擦，但增加了双层PtN中的层间摩擦，并且在表面功能化下，层间摩擦可以通过面外极化有效地调节。有趣的是，与本征双层MgN相比，HBr - MgN的摩擦系数低两个数量级，导致一种类似于超润滑的现象。这些结果极大地有助于我们对摩擦性能的理解，为MN在固体润滑剂中的实际应用提供了有价值的指导。
