Nanoscale Friction Control in Transition Metal Dichalcogenides

One of the main difficulties in understanding and predicting frictional response is the intrinsic complexity of highly non-equilibrium processes in any tribological contact.

To understand the physical nature of the microscopic mechanism of friction and design new tribologic materials, we conducted a systematic quantum mechanic investigation on prototipical Van der Waals MX₂ (M=Mo, W; X=S, Se, Te) Transition Metal Dichalcogenides. We combined structural and dynamic information from group theory and phonon calculations with electronic features using non-standard methods such us orbital polarization, bond covalency and cophonicity analyses. We propose a phonon-mode based method to identify possible sliding paths, to tune the corresponding sliding energy barriers and to characterize and control frictional/dissipation energy channels. We discuss how to extract information on the energetics of sliding from atomic force microscopy signals. We finally formulate guidelines on how to engineer intrinsic friction at the nanoscale in order to design novel materials with expected improved tribological properties.

The present outcomes can be promptly used to finely tune physical properties for the design of new materials with diverse applications beyond tribology.