Superlubricity achieved for commensurate sliding: MoS2 frictional anisotropy in silico

In the past decades, MoS2 has received substantial attention from the tribology community due to its excellent frictional properties. However, a fundamental understanding of the mechanisms determining friction at the nanoscale is yet to be achieved. The general consensus is that one of the ingredients required for obtaining the superlubric regime when sliding layers of MoS2 atop each other is incommensurability. Herein, we report on a molecular dynamics study focused on studying the effects of the sliding direction on the frictional properties of commensurate MoS2. It is found that different types of dynamics are obtained with different sliding directions, with the stick-slip dynamics characterized by a highly dissipative behavior. Also, it is found that there is a relation linking the mismatch angle between the driving force and the actual trajectory and the load-dependence of the frictional force. We show, for the first time with a computational study, that incommensurability is not required for achieving the superlubric behavior of MoS2.