**Computational Study of Low Interlayer Friction in Tin+1Cn (n=1, 2, and
3) MXene**

DF Zhang and M Ashton and A Ostadhossein and ACT van Duin and RG Hennig and SB Sinnott, ACS APPLIED MATERIALS & INTERFACES, 9, 34467-34479 (2017).

DOI: 10.1021/acsami.7b09895

The friction of adjacent Tin+1 C-n (n = 1, 2, and 3) MXene layers is investigated using density functional theory (DFT) calculations and classical molecular dynamics simulations with ReaxFF potentials. The calculations reveal the sliding pathways in all three MXene systems with low energy barriers. The friction coefficients for interlayer sliding are evaluated using Static calculations. Both DFT and ReaxFF methods predict friction coefficients between 0.24 and 0.27 for normal loads less than 1.2 GPa. The effect of titanium (Ti) vacancies in sublayers and terminal oxygen (0) vacancies at surfaces on the interlayer friction is further investigated using the ReaxFF potential. These defects are found to increase the friction coefficients by increasing surface roughness and creating additional attractive forces between adjacent layers. However, these defective MXenes still maintain friction coefficients below 0.31. We also consider functionalized Ti3C2 MXene terminated with -OH and -OCH3 and find that compared to the O-terminated further reduce the interlayer friction coefficient to 0.10-0.14. surface both groups

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