Effect of Surface Stiffness on the Friction of Sliding Model Hydroxylated α-Alumina Surfaces

Abstract

Molecular dynamics simulations were performed to determine how interfacial properties and friction forces of two model hydroxylated α-alumina surfaces are affected by softening or stiffening the surface potential, without changing the surface−surface intermolecular potential Vinter. The surface−surface vibrational spectrum for the soft surface, in absence of applied load, is influenced by coupling between Vinter and the surface vibrations. For the stiff surface, this coupling becomes important as the applied load is increased. Friction forces for the stiff and soft surfaces are similar at low loads, but at high loads the stiff surface has higher friction forces. This result mirrors the surface−surface vibrational spectra for the soft and stiff surfaces versus load. Increasing the load forces both systems into potential energy wells, requiring additional energy (or external force) to surmount potential energy barriers for sliding, leading to enhanced friction. At high sliding velocity, the instantaneous ba...