Augmented Fourier components method for constructing the crystal potential in self-consistent band-structure calculations

We describe a method to perform self-consistent band structure calculations. This combination of the extended linear augmented plane wave (ELAPW)-kp method with a plane-wave basis set offers a scheme to construct the crystal potential alternative to the well-known full-potential linear augmented plane wave (FLAPW) technique. We propose a representation of the crystal density that is free from unphysical computational parameters specific to the: representation of the wave functions. The valence density is divided into two parts, one of which is expanded in a Fourier series and the other one is localized within small spheres surrounding the nuclei. It is shown that to a good approximation the latter part can be represented by its Y-00 component. The quality of the representation is controlled by the number of Fourier components of the density, and the computational effort can be balanced with the desired accuracy. By construction the density is smooth everywhere in the unit cell. The technique of constructing the potential, the augmented Fourier components method (AFC), is described. The properties of the method are demonstrated using the cubic semiconductors Si, SiC, GaAs, BaTiO3, KNbO3, KTaO3, and metallic 1T chalcogenides TiS2 and TiSe2 as examples. The self-consistent density-of-states curves are presented. With the AFC ELAPW-kp method optical properties of TiSe2 are calculated; complex dielectric function and reflectivity are in good agreement with experimental results. [S0163-1829(99)08315-0].