Crystalline Ni(3)C as both carbon source and catalyst for graphene nucleation: a QM/MD study

Graphene nucleation from crystalline Ni(3)C has been investigated using quantum chemical molecular dynamics (QM/MD) simulations based on the self-consistent-charge density-functional tight-binding (SCC-DFTB) method. It was observed that the lattice of Ni(3)C was quickly relaxed upon thermal annealing at high temperature, resulting in an amorphous Ni(3)C catalyst structure. With the aid of the mobile nickel atoms, inner layer carbon atoms precipitated rapidly out of the surface and then formed polyyne chains and Y-junctions. The frequent sinusoidal-like vibration of the branched carbon configurations led to the formation of nascent graphene precursors. In light of the rapid decomposition of the crystalline Ni(3)C, it is proposed that the crystalline Ni(3)C is unlikely to be a reaction intermediate in the CVD-growth of graphene at high temperatures. However, results present here indicate that Ni(3)C films can be employed as precursors in the synthesis of graphene with exciting possibility.