Calculation of optical properties and density of states for systems with huge unit cells - art. no. 035105

Citation
Hc. Weissker et al., Calculation of optical properties and density of states for systems with huge unit cells - art. no. 035105, PHYS REV B, 6403(3), 2001, pp. 5105
Citations number
28
Categorie Soggetti
Apllied Physucs/Condensed Matter/Materiales Science
Journal title
PHYSICAL REVIEW B
ISSN journal
01631829 → ACNP
Volume
6403
Issue
3
Year of publication
2001
Database
ISI
SICI code
0163-1829(20010715)6403:3<5105:COOPAD>2.0.ZU;2-9
Abstract
We present a method for the ab initio calculation of spectral properties of systems with huge unit cells. Translationally invariant systems with eleme ntary cells containing several hundred atoms in the unit cell are character ized by a large number of bands in a very small Brillouin zone. This makes the allocation of energies at different k points to one band impossible. Fo r that reason a quadratic extrapolation of the band energies is performed s tarting from a single k point k(o). The band energies and momentum operator matrix elements are calculated at ko using the projector augmented wave me thod. The Brillouin-zone integration is carried out by means of the linear tetrahedron method following a resampling procedure. The viability of the m ethod is demonstrated for nonprimitive large supercells by reproducing the absorption coefficient and the density of states of an ideal crystal. The m ethod is applied to 216- and 512-atom simple-cubic supercells. A germanium cluster embedded in a host material is treated as an example of a perturbed system.