Numerical investigations into mechanical properties of hexagonal silicon carbon nanowires and nanotubes.

Single-crystalline hexagonal faceted silicon carbon nanowires and nanotubes possess simultaneous high strength and failure strain. As long as SiC nanowires or nanotubes are large or thick enough to sustain a single atomic configuration under loading, their mechanical properties are size independent. Surface atoms are firstly forced to move by stretching and then destroy the equilibrium of subsurface atoms. Then, the force in carbon-silicon bonds along the tensile directions becomes larger than that in other bonds and results in elongation by three-times of the former than that of the latter. However, the latter bonds connecting the surface to the subsurface are broken and the wires or tubes are ruptured. For thinner nanowires and nanotubes, the broken bonds don't propagate instantly, but initiate transformation from a wurtzite to a graphitic structure. This structure transformation can strengthen and plasticize SiC nanowires and nanotubes.