A numerical study of the imperfection effect on ultrananocrystalline diamond properties under different loading paths and temperatures

To better understand the imperfection influence on the ultrananocrystalline diamond (UNCD) properties under various loading conditions, a numerical study is performed to investigate the effect of vacancies on the mechanical responses of pure and nitrogen (N)-doped UNCD films under tensile and shear loading paths at elevated temperatures. A simple procedure is developed by combining kinetic Monte Carlo with molecular dynamics (MD) methods to form a polycrystalline UNCD block. Different numbers of vacancies are introduced by randomly removing carbon atoms from the resulting UNCD blocks. The responses of the simulated pure and N-doped UNCD blocks with different numbers of vacancies are then investigated by applying displacement–controlled loading under different temperatures in the MD simulations. The simulation results presented in this paper provide a better understanding of the imperfection effect on the mechanical responses of pure and N-doped UNCD films as compared with the grain boundary effect.