**Load- and Size Effects of the Diamond Friction Coefficient at the
Nanoscale**

HZ Liu and WJ Zong and X Cheng, TRIBOLOGY LETTERS, 68, 120 (2020).

DOI: 10.1007/s11249-020-01360-3

The friction coefficient, an important parameter to evaluate the dynamic
properties of friction pairs, has been widely used in macro engineering
fields. However, it is probably inappropriate to characterize the
tribological properties at the nanoscale due to the strong size effect,
and the conventional formula cannot reveal its determinants owing to its
oversimple form. Therefore, in the present work, a new formula is
deduced to overcome these shortcomings. The established formula for the
friction coefficient considers the adhesion and discloses the
relationship between the friction coefficient and the material
properties of diamond. It effectively suppresses the dependency of the
friction coefficient on the load, although such a dependency cannot be
eliminated completely. Therefore, another new formula, independent of
the loading force, is derived. Interestingly, the results indicate that
the size effect is invariably observed in the friction coefficients
derived from the three formulas due to different accumulation effects of
debris atoms, which is verified by molecular dynamics simulations.
**GRAPHICS** .

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