First-principles electronic structure of Si, Ge, GaP, GaAs, ZnS, and ZnSe. II. Optical properties

Elementary energy bands in isovalent IV–VI orthorhombic and cubic crystals and their solid solutions

“…Consequently, one can make an obvious conclusion that the point where the accumulation of valence electrons is observed in the unit cell of the cubic crystals like Si, Ge and diamond with prevailing covalent bonding is a middle point between two neighboring atoms. The calculations of the spatial electron density distribution in these crystals [32] confirm these conclusions.…”

“…This situation is observed in the elementary IV-group semiconductors like Ge and Si [31,32]. As is well known, the symmetry of these crystals is described by the space group 7 h O (Fd3m ).…”

Fcenter in lithium fluoride revisited: Comparison of solid-state physics and quantum-chemistry approaches

“…These calculations are either based on densityfunctional theory (DFT) [15,16] treating the extended system using periodic boundary conditions, or on quantum-chemical methods [16][17][18][19] explicitly treating a cluster. Previous DFT calculations were based on the local-density approximation (LDA) suffering from the well known underestimate of the band gap for insulators [20][21][22] and the unphysical delocalization of localized states. Another problem in previous calculations is the use of the independent-particle approximation within which the electron-hole interaction is not properly accounted for in the determination of the excitation energies of the F center.…”

Electronic structure and optical properties ofZnX(X=O,S, Se, Te): A density functional study

“…Density-functional theory (DFT) 16 in the local-density approximation (LDA) 17 has also been used to calculate optical spectra for ZnO-w 18 and ZnS-w 18 by linear combination of atomic orbitals, and for ZnS-z 19 and ZnSe-z 19 by self-consistent linear combination of Gaussian orbitals. The optical spectra of ZnO (including excitons) has been investigated 20 by solving the Bethe-Salpeter equation.…”

“…Other considered approaches for ab initio computations of optical properties involve electron-hole interaction, 41 partial inclusion of dynamical vertex corrections that neglect excitons, 42 and empirical energy-dependent self-energy correction according to the Kohn-Sham local density theory of excitation. 19 However, the simplest method is to apply the scissor operator, 43 which displaces the LDA eigenvalues for the unoccupied states by a rigid energy shift. Using the latter method excellent agreement with experiments has been demonstrated for lead monochalcogenides 44 and ferroelectric NaNO 2 .…”