Nanoindentation and scratching behaviors of diamond-like carbon films by coarse-grained molecular dynamics

High-performance coatings such as diamond-like carbon (DLC) films own thin thickness which is in the gap of experiment and molecular dynamics (MD), limiting the measurement of their intrinsic mechanical properties. To achieve the direct comparison between experiment and simulation, modified parameters of Tersoff potential describing the interaction among amorphous carbon accurately are proposed for coarse-grained MD simulations of DLC films. Such parameters are validated in compression and shear loadings compared with all-atom MD. A fitted mathematical contact model of the actual contact depth of indenter in nanoindentation is studied. By using this model, the elastic moduli of DLC films have been computed and the effect of relaxation is discussed. Besides magnified dimensions, the larger mass of coarse-grained beads enables the greater time interval, realizing the friction simulation of DLC films at experimental sliding velocities, and giving a methodological inspiration for the studies of mesoscopic simulations of amorphous materials.