Molecular dynamics simulation of nanoscale mechanical behaviour of ZnO under nanoscratching and nanoindentation

Molecular dynamics is used to simulate the mechanical behaviour of zinc oxide under nanoscratching and nanoindentation. The effects of indenter speed and substrate temperature on the structure-phase formation, slip vector, radial distribution function, and residual stresses are investigated. Simulation results show that the dislocation loops nucleate and propagate, forming a body-centred tetragonal lattice structure along the slip direction due to high local stress. Furthermore, the dislocation loops nucleate and propagate due to the resolved shear stress along the 45 degrees slip direction under nanoscratching. The average mean biaxial stress and the normal stress of the O layers are -9.35 and -4.36 GPa, respectively, and those of the Zn layers are -0.80 and -0.30 GPa, respectively. This may be attributed to the energetic O atoms, with which unstable atoms have high activation.