Crystalline Ni₃C as both carbon source and catalyst for graphene nucleation: a QM/MD study

Graphene nucleation from crystalline Ni₃C 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 Ni₃C was quickly relaxed upon thermal annealing at high temperature, resulting in an amorphous Ni₃C 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 Ni₃C, it is proposed that the crystalline Ni₃C is unlikely to be a reaction intermediate in the CVD-growth of graphene at high temperatures. However, results present here indicate that Ni₃C films can be employed as precursors in the synthesis of graphene with exciting possibility.