Atomic-Scale Superlubricity in Ti₂CO₂@MoS₂ Layered Heterojunctions Interface: A First Principles Calculation Study

The two dimensional (2D)-layered transition-metal carbides and nitrides (MXene) have been proved to be an excellent solid lubricant owing to their high mechanical strength, low shearing strength, and self-lubricating properties. However, the interfacial friction behavior between Ti C (n = 1, 2) MXene and its heterogeneous system is not thoroughly exploited yet. Here, four types of van der Waals structures (Ti₂CO₂@Ti₂CO₂, Ti₃C₂O₂@Ti₃C₂O₂ MoS₂@MoS₂, and Ti₂CO₂@MoS₂) have been investigated by density functional theory (DFT) calculations. The results exhibit that Ti₂CO₂@MoS₂ possesses the lowest sliding energy barrier around 0.015 eV/oxygen(O) atom compared with the other three constructed models. Therefore, this work mainly focuses on the inner relation of Ti₂CO₂@MoS₂ interlayer friction behaviors and its attributing factors, including normal force and charge density. The DFT analysis shows that the roughness of the potential energy corrugated plane is positively correlated with normal force and predicted the ultralow friction coefficient (μ) at 0.09 when sliding along the minimum energy potential route. Moreover, friction coefficient fluctuates at the normal force less than 10 nN determined by the combined effect of interfacial charge interlock and redistribution. This work reveals the intrinsic connection between the friction and charge interaction at heterogeneous interfaces.