First-principles study of the electronic properties of simple hexagonal graphite

The electronic properties of simple hexagonal graphite have been studied in the framework of the density-functional technique, using nonlocal ionic pseudopotentials and a large number of plane waves. This work leads to a first-step qualitative understanding of the electronic properties of nonperiodic structures such as pregraphitic and disordered carbons (turbostratic graphite), which are composed of periodic regions of simple hexagonal graphite surrounded by domains of the usual (Bernal) form of graphite. Particular attention has been paid to the comparison with the properties of the Bernal graphite. The valence charge density, the density of states, the band structure, as well as a description of the electronic energies at the Fermi level are provided. The latter is parametrized by a tight-binding model, and compared to the Slonczewski-Weiss-McClure model of Bernal graphite electronic energies. The Fermi surface is calculated and an exchange of hole and electron pockets between these two forms of graphite is observed. The behavior of electronic energies under pressure, and the associated deformation potentials, are also studied.