Band Structure and Fermi Surface of Rhombohedral and Simple Graphites

Abstract

Using ab-initio calculation, we have computed the band structure, Fermi surface and other electronic parameters associated with the transport coefficients of graphite for different stackings of carbon layers. Software CRYSTAL was used with a Pople standard STO-21G* basis set. Different Hamiltonians were tested, choosing a restricted Hartree-Fock one, because it generated the best qualitative results. All graphites studied present a valence bandwidth, near 0.60 a.u., in agreement with the literature. Single layer graphites generate two Π bands around of the Fermi level (EF = —0.438 a.u.). Four Π bands, one being degenerate, appear in hexagonal 3D simple graphite, EF being equal to —0.00954 a.u. In hexagonal Bernal graphite the splitting of the valence Π band was accentuated, and EF = —0.00140 a.u. Rhombohedral graphite shows a band structure slightly different, with EF = 0.0381 a.u. Important differences between band structures are reported in the HKH edge according to stacking of graphite layers. The Fermi surface for each graphite type is located near the P point (single layer) or around the HKH edge of the first Brillouin zone (3D graphite). In general such surfaces present a central electron orbit of maximal size in the plane, which diminishes in size when the z component of the k vector moves in KH direction.