Structural and Electronic Properties of Graphene and Silicene: An FP-(L)APW+lo Study

We report here the structural and electronic properties of graphene and silicene (silicon analogue of graphene) investigated using first-principles calculations of their ground state energies employing full-potential (linearized) augmented plane wave plus local orbital (FP-(L)APW+lo) method. On structure optimization, we found that the graphene-like honeycomb structure of Si is buckled (buckling parameter $\Delta = 0.44$ \AA in constrast with graphene whose structure is planar ($\Delta = 0.0$ \AA). In spite of the buckled-structure, silicene has an electronic structure similar to that of graphene. The results are in agreement with previous reports based on other methods. We have also calculated the lower bounds of the lattice constant $"a"$ of these 2D systems, within the present method of study which are our new results.