Tribology - the science of friction, wear, and lubrication - is of fundamental importance in many branches of pure and applied science. One of the most intriguing concepts of modern tribology, with exciting practical applications, is the idea of frictionless interface sliding in incommensurate contacts, a phenomenon termed superlubricity. Until very recently, observations of superlubric behavior have been limited to nano- and micro-scale graphitic contacts. One of the major problems in achieving superlubricity using such homogeneous graphitic contacts stems from the fact that graphene tends to spontaneously lock into high-friction states that suppress superlubricity. This fundamental problem has been resolved in our recent studies predicting theoretically and computationally, and thereafter demonstrating experimentally, that microscale heterogeneous layered material junctions exhibit robust superlubricity under ambient conditions and room temperature.

In this talk I will discuss results of fully atomistic numerical simulations of static and dynamical properties of graphite/graphite and graphite/hexagonal boron nitride (h-BN) junctions. We found that structural superlubricity at interfaces between graphite and h-BN persists even for the aligned contacts sustaining external loads. A negative friction coefficient, where friction is reduced upon increasing normal load, was predicted. It was demonstrated that further control over the physical properties of 2D layered materials can be gained via tuning the aspect-ratio of nanoribbons.

Scaling up structural superlubricity towards macroscopic dimensions inevitably involves forming junctions between surfaces of polycrystalline nature. The effects of corrugated grain boundaries on the frictional properties of extended planar graphitic contacts incorporating a polycrystalline surface were investigated via molecular dynamics simulations. This study revealed that collective dynamic effects at polycrystalline graphite grain boundaries may lead to unusual nonmonotonic variation of the friction with normal load and temperature. Our results are expected to be of general nature and should be applicable to other van der Waals heterostructures.