  Stone-Wales (SW) defects are favorably existed in graphenelike materials with
honeycomb lattice structure and potentially employed to change the electronic
properties in band engineering. In this paper, we investigate structural and
electronic properties of SW defects in bulk silicene and its nanoribbons as a
function of their concentration using the methods of periodic boundary
conditions with first-principles calculations. We first calculate the formation
energy, structural properties, and electronic band structures of SW defects in
bulk silicene, with dependence on the concentration of SW defects. Our results
show a good agreement with available values from the previous first-principles
calculations. The energetics, structural aspects, and electronic properties of
SW defects with dependence on defect concentration and location in
edge-hydrogenated zigzag silicene nanoribbons are obtained. For all calculated
concentrations, the SW defects prefer to locate at the edge due to the lower
formation energy. The SW defects at the center of silicene nanoribbons slightly
influence on the electronic properties, whereas the SW defects at the edge of
silicene nanoribbons split the degenerate edge states and induce a sizable gap,
which depends on the concentration of defects. It is worth to find that the SW
defects produce a perturbation repulsive potential, which leads the decomposed
charge of edge states at the side with defect to transfer to the other side
without defect.
