Nanotribological Properties of the h‑BN/Au(111) Interface: A DFT Study

Understanding
the quantum-mechanical origins of friction forces has become increasingly
important in the past decades with the advent of nanotechnology. At
the nanometer scale, the universal Amontons–Coulomb laws cease
to be valid, and each interface requires individual scrutiny. Because
of the well-known lubricating properties of two-dimensional materials,
a significant amount of research has been performed in an effort to
understand interfaces they form with one another. However, the interfaces
between these two-dimensional materials and metals red from a tribological
point of view, important for such applications as friction force microscopy,
have yet to be thoroughly investigated. In the current work, we present
a detailed density functional theory investigation of the hexagonal
BN/Au(111) interface. Because of a good agreement between their characteristic
lengths, a high level of commensurability is achieved in a suitably
constructed model between the bulk surfaces of the two materials.
As a result of our calculations, we find that the corrugation in the
potential energy surface and the lateral forces in this interface
are low compared to other similar interfaces. The friction coefficient
falls rapidly with increasing load down to 0.005 for the largest loads
considered. In contrast, Aun clusters
(n = 1, 4, 13, and 19) sliding on the h-BN surface
exhibit much larger lateral forces, indicating strong size and edge
effects. The reduction of energy corrugation in going from the Au4 to the Au19 cluster may already indicate a decreasing
trend with increasing size even at this very small scale.