Molecular Dynamics Simulation of Lubricant Adsorption and Thermal Depletion Instability

In this work, we incorporated a quartic bond potential into a coarse-grained bead-spring model to study lubricant adsorption on a solid surface as well as depletion instability. The surface tension density and the number density profiles were examined to verify the solid-liquid and liquid-vapor interfaces during heat treatment. It was found that both the liquid-vapor interfacial thickness and the solid-vapor separation increase with the temperatureT when Tis below the phase transition temperature Tc. At high temperatures (T>Tc), the solid-vapor separation decreases gradually as the temperature increases. In addition, we evaluated the lubricant weight and bond loss profiles at different temperatures. It was observed that the lubricant desorption is favored over decomposition and is the main cause of the lubricant failure at the head disk interface in our simulations. Keywords—Depletion instability, Lubricant film, Thermal adsorption, Molecular dynamics (MD).