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Liquid crystals have emerged as potential candidates for next-generationlubricants due to their tendency to exhibit long-range ordering. Here, weconstruct a full atomistic model of 4-cyano-4-hexylbiphenyl (6CB) nematicliquid crystal lubricants mixed with hexane and confined by mica surfaces. Weexplore the effect of the surface structure of mica, as well as lubricantcomposition and thickness, on the nanoscale friction in the system. Our resultsdemonstrate the key role of the structure of the mica surfaces, specificallythe positions of potassium ($\mathrm{K}^+$) ions, in determining the nature ofsliding friction with monolayer lubricants, including the presence or absenceof stick-slip dynamics. With the commensurate setup of confining surfaces, whenthe grooves created between the periodic $\mathrm{K}^+$ ions are parallel tothe sliding direction we observe a lower friction force as compared to theperpendicular situation. Random positions of ions exhibit even smaller frictionforces with respect to the previous two cases. For thicker lubrication layersthe surface structure becomes less important and we observe a good agreementwith the experimental data on bulk viscosity of 6CB and the additive hexane. Incase of thicker lubrication layers, friction may still be controlled by tuningthe relative concentrations of 6CB and hexane in the mixture.

Nanoscale Liquid Crystal Lubrication Controlled by Surface Structure and Film Composition