Ah initio Plane Wave Self Consistent study of the electronic dispersion for graphene and a (5, 5) SWCNT

摘要

We study the electronic dispersion for a graphene sheet and also a (5, 5) single wall carbon nanotube (SWCNT) by using PWscf (Plane Wave self consistent field) code from "quantum espresso" package. Two different pseudopotentials, "norm conserving" and "ultra soft", has been employed and the results are more or less similar. By energy relaxation, it was found that, if in a graphite lattice the interlayer distance expands up to 4.5 times of the in-layer (hexagons) lattice constant then, each layer can be considered as an individual graphene sheet, and also for a bundle of (5, 5) SWCNTs, the optimum distance between the tubes is about 19 a.u and for a single tube consideration, this distance is about 22 a.u. The calculated band structure and density of states (DOS) for the tube, shows in the vicinity of Fermi level there is no energy gap (so it is metallic) and there is a general agreement between them and Zone Folding (Z F) studies or other ab-initio methods in literatures. Curvature effects on the band shifts and DOS has been under consideration also.