Molecular dynamics simulation for plastic deformation mechanisms of single crystal diamond during nanoindentation

The elastic-plastic deformation mechanism of single crystal diamond under spherical nanoindentation was emphasised using molecular dynamics (MD). The benchmark tests to determine the empirical potential that accurately describe the interactions between diamond atoms were completed. Tensile strength of diamond at different temperatures was studied under the empirical potential preferentially selected by benchmark tests. The nanoindentation process of the diamond is subsequently carried out on the surface (001). Plastic deformation behaviour of brittle diamond was found, such as amorphisation, phase transformation, graphitisation and dislocation evolution were analysed and discussed using combined methods. The simulation results show that the plastic deformation behaviour of the diamond material is also evident, even though diamond is a brittle material with high strength and hardness. 'Pop-in' event of the P-h curve is the turning point from elastic to plastic deformation. The elastic stage can be divided into the pure elastic and the quasi-elastic deformation stages. The plastic deformation behaviour of diamond is dominated by a combination of phase transformation, graphitisation and dislocation nucleation. It is also found that the primary dislocation type is 1/2<110> perfect dislocation, which was distributed in the area of large stress concentration below the indenter.