Molecular dynamics simulations of faceting of silicon carbide nanoparticles

Equilibrium shapes of crystals can be calculated using Wulff construction. However, kinetic barriers can prevent a system from realizing its equilibrium shape. On the basis of a simple model, Mullins predicted that nanoparticles can be kinetically immobilized so that normal motion of facets does not happen, prohibiting the nanoparticle from realising its equilibrium shape. Using molecular dynamics simulations, we obtain the equilibrium shape of silicon carbide nanocrystals (n-SiC) from an initially spherical shape. During a 300 nanoseconds simulation at 2200 K, an 8 nm particle of SiC-3C transforms from its initial spherical shape to a rhombic dodecahedron. Furthermore, by performing multiple simulations – a total of 40 µs – of initially cylindrical SiC nanoparticles, we identify energy barriers to facet growth normal to facet planes. We find that the energy barrier to normal growth of facets on n-SiC is higher than in Mullins’ model, but we still observe normal motion of the facets. The final shapes of SiC nanoparticles are independent of the initial configuration when the temperature is sufficiently high to overcome the facet growth barrier.