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

Area of Science:

• Materials Science
• Tribology
• Surface Chemistry

Background:

• Two-dimensional (2D) transition-metal carbides and nitrides (MXenes) are recognized for their potential as solid lubricants due to inherent mechanical strength and low shear properties.
• The tribological behavior of MXenes, particularly in heterogeneous systems, remains underexplored, limiting their application in advanced lubrication technologies.

Purpose of the Study:

• To investigate the interfacial friction mechanisms of van der Waals heterostructures involving Ti2CO2 MXene and MoS2.
• To determine the factors influencing friction, such as normal force and charge density, in Ti2CO2@MoS2 systems.

Main Methods:

• Density Functional Theory (DFT) calculations were employed to model and analyze four distinct van der Waals structures.
• Calculations focused on sliding energy barriers, potential energy surface roughness, and interfacial charge distribution.
• Analysis included the correlation between normal force and friction behavior.

Main Results:

• The Ti2CO2@MoS2 heterostructure demonstrated the lowest sliding energy barrier (0.015 eV/O atom) among the studied models.
• An ultralow friction coefficient (μ) of 0.09 was predicted for Ti2CO2@MoS2 under optimal sliding conditions.
• Friction coefficient fluctuations at low normal forces (<10 nN) were attributed to interfacial charge interlock and redistribution.

Conclusions:

• Ti2CO2@MoS2 exhibits exceptional solid lubrication properties, driven by favorable interfacial charge interactions.
• Normal force significantly influences the potential energy landscape and thus the friction behavior at the interface.
• This study elucidates the fundamental link between charge dynamics and friction in heterogeneous 2D material systems.