Large-scale molecular-dynamics simulations were employed to study defect generation and primary damage state in nanocrystalline SiC of average grain diameters from 5 to 21nm. Primary knock-on atom kinetic energies of 10keV were simulated and cascade structures in nanocrystalline SiC with a grain size smaller than 12nm were generally different from those generated in single-crystalline SiC. It was found that the local stresses near the grain boundaries strongly affect the behaviour of the primary knock-on atom and secondary recoil atoms, and the grain boundaries act as sinks for deposition of kinetic energy. A striking feature was that the primary knock-on atom and secondary recoil atoms preferentially deposit energy along the grain boundaries for grains with average size less 12nm, which results in atomic displacements primarily within the grain boundaries; whereas for larger grain sizes, most defects were produced within the grains. The defect production within gains generally increased with increasing grain size, which was manifested in switching from grain boundary damage to grain damage. The most common defects created in nanocrystalline SiC were antisite defects, following by vacancies and interstitials, in contrast to those produced in a single-crystalline SiC, where the dominate defects were Frenkel pairs. Defect production efficiency increased with increasing grain size, with a typical value of 0.18 for small grains and rising to 0.5 for larger grains

Energy Dissipation and Defect Generation in Nanocrystalline Silicon Carbide. F.Gao, D.Chen, W.Hu, W.J.Weber: Physical Review B, 2010, 81[18], 184101