Augmented Fourier components method for constructing the crystal potentialin 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 m ethod with a plane-wave basis set offers a scheme to construct the crystal potential alternative to the well-known full-potential linear augmented pla ne wave (FLAPW) technique. We propose a representation of the crystal densi ty that is free from unphysical computational parameters specific to the: r epresentation of the wave functions. The valence density is divided into tw o 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 compone nt. The quality of the representation is controlled by the number of Fourie r components of the density, and the computational effort can be balanced w ith the desired accuracy. By construction the density is smooth everywhere in the unit cell. The technique of constructing the potential, the augmente d Fourier components method (AFC), is described. The properties of the meth od are demonstrated using the cubic semiconductors Si, SiC, GaAs, BaTiO3, K NbO3, 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 fu nction and reflectivity are in good agreement with experimental results. [S 0163-1829(99)08315-0].