Molecular Dynamics Simulations of Nanoindentation and Nanoscratching of $\beta$-SiC

We present the results of molecular dynamics simulations of nanoindentation of the Si-terminated (001) surface of $\beta$-SiC by a diamond tip. In particular we investigate the dependence of the critical depth and pressure for the elastic-to-plastic transition as a function of indentation velocity, tip size, and workpiece temperature. Our simulations were carried out using the Tersoff potential, which accurately reproduces the lattice and elastic constants of $\beta$-SiC. Over the range of indenter sizes used in our simulations, both the critical pressure and indentation depth decrease with increasing indenter size. In contrast, the critical indentation depth for the elastic-to-plastic transition does not depend on the indenter velocity. For indentation depths beyond the critical depth, the pressure saturates at 100 GPa, which corresponds to the experimental pressure at which $\beta$-SiC transforms to the rocksalt structure. An analysis of the pair-correlation function and bond-angle distribution as a function of indenter depth supports our conjecture that the observed plastic behavior is related to the onset of a phase transition from the zinc-blende structure to the rocksalt structure. Results for nanoscratching of the (100) surface of $\beta$-SiC are also presented.