Optimized geometry and electronic structure of graphyne-like silicyne nanoribbons

Silicyne, a silicon allotrope, which is closely related to silicene and has graphyne-like structure, is theoretically investigated in this work. Its optimized geometry and electronic band structure are calculated by means of the first-principles frozen-core projector-augmented wave method implemented in the Vienna ab initio simulation package (VASP). We find that the lattice parameter is 9.5 angstrom, the silicon chain between hexagons is composed of disilynic linkages (-Si equivalent to Si-) rather than cumulative linkages (=Si=Si=), and the binding energy is -3.41 eV per atom. The band structure is calculated by adopting the generalized gradient approximation and hybrid functionals. The band gap produced by the HSE06 functional is 0.73 eV, which is nearly triple that by the generalized gradient approximation of Perdew-Burke-Ernzerhof functional.