The Fascinating Frictional Properties of Layered Materials
Oded Hod, School of Chemistry, Tel Aviv University
Structural superlubricity may provide a viable route for significant reduction of friction and wear. In this talk, I will present results of fully atomistic numerical simulations of unique static and dynamical properties exhibited by graphite/hexagonal boron nitride (h-BN) heterojunctions, performed using a dedicated anisotropic inter-layer potential recently developed in our group.
I will demonstrate how structural superlubricity at interfaces formed between graphite and h-BN persists even at aligned microscale contacts sustaining external loads. I will underline the conditions required for achieving negative friction coefficients - a state where friction is reduced upon increasing normal load. Nanoscale demonstrations of the “princess and the pea” problem and the motion of nanoserpents will be briefly discussed. The tribological properties associated with motion over grain boundaries appearing in large-scale polycrystalline surfaces will be presented. I will further show intriguing parity dependence of moiré superstructures occurring at heterogeneous layered materials interfaces and controllable heat flow through twisted layered materials junctions. Should time permit, I will demonstrate a friction-based classical analogue of the chiral induced spin selectivity effect.
 W. Ouyang, O. Hod, and M. Urbakh, "Parity-Dependent Moiré Superlattices in Graphene/h-BN Heterostructures: A Route to Mechanomutable Metamaterials", Phys. Rev. Lett., in press (2021).
 X. Gao, W. Ouyang, O. Hod, and M. Urbakh, "Mechanisms of Frictional Energy Dissipation at Graphene Grain Boundaries", Phys. Rev. B 103, 045418 (2021).
 W. Ouyang, H. Qin, M. Urbakh, and O. Hod, "Controllable Thermal Conductivity in Twisted Homogeneous Interfaces of Graphene and Hexagonal Boron Nitride", Nano Lett. 20, 7513-7518 (2020).
 W. Ouyang, I. Azuri, D. Mandelli, A. Tkatchenko, L. Kronik, M. Urbakh, and O. Hod, "Mechanical and Tribological Properties of Layered Materials Under High Pressure: Assessing the Importance of Many-Body Dispersion Effects", J. Chem. Theory Comput., J. Chem. Theory Comput. 16, 666-676 (2020).
 D. Mandelli, W. Ouyang, M. Urbakh, and O. Hod, "The Princess and the Nanoscale Pea: Long-Range Penetration of Surface Distortions into Layered Materials Stacks", ACS Nano 13, 7603-7609 (2019).
 D. Mandelli, W. Ouyang, O. Hod, and M. Urbakh, "Negative Friction Coefficient in Superlubric Graphite/Hexagonal Boron Nitride Heterojunctions", Phys. Rev. Lett. 122, 076102 (2019).
 O. Hod, E. Meyer, Q. Zheng, and M. Urbakh, "Structural Superlubricity and Ultralow Friction Across the Length Scales", Nature 563, 485-492 (2018).