Atomistic simulations of hard and soft films under nanoindentation

Three-dimensional molecular dynamics (MD) simulation is used to investigate the atomistic mechanism of nanoindentation process under different indentation loads, temperatures and loading rates. Diamond and gold were selected as the hard and soft materials. The results showed that when the loads and the loading rates increased, both Young's modulus and the hardness of the films were increased. When the nanoindentation was operating under high temperatures, the thermal softness behavior took place causing a reduction in Young's modulus. The hardness for diamond and gold films was approximately 90–100 GPa and 3–5 GPa, while the present MD analysis for diamond and gold films was found to be 84–107 GPa and 5–7 GPa, respectively. Young's modulus for the diamond and gold films were approximately 1002–1100 GPa and 110–130 GPa, while the present MD analysis for diamond and gold films was found to be 1199–1862 GPa and 78–129 GPa, respectively. Both Young's modulus and the hardness were slightly higher than those in the experiments. The discrepancy between the MD analysis and the experiments will be further discussed in this paper.