Microstructural and elastic properties of silicon-germanium-carbon alloys

We present a theoretical study, based on Monte Carlo simulations, of the equilibrium structure and elastic properties of Si1−x−yGexCy alloys. We find a repulsive interaction among C substitutionals at short separations and, consistently with previous work, a preferred third nearest-neighbour-atom arrangement. Very few GeC bonds are found. We also observe significant deviations of the structural parameters of the system from linearly interpolated values. This effect is linked to a considerable downward bowing of the elastic constants of the material, as C is added.