Ga+, In+, and Tl+ impurities in alkali halide crystals: Distortion trends

Cu-Doped KCl Unfolded Band Structure and Optical Properties Studied by DFT Calculations

The unfolded band structure and optical properties of Cu-doped KCl crystals were computed by first principles within the framework of density functional theory, implemented in the ABINIT software program, utilizing pseudopotential approximation and a plane-wave basis set. From a theoretical point of view, Cu substitution into pristine KCl crystals requires calculation by the supercell (SC) method. This procedure shrinks the Brillouin zone, resulting in a folded band structure that is difficult to interpret. To solve this problem and gain insight into the effect of copper ions (Cu+) on electronic properties, the band structure of SC KCl:Cu was unfolded to make a direct comparison with the band structure of the primitive cell (PC) of pristine KCl. To understand the effect of Cu substitution on optical absorption, we calculated the imaginary part of the dielectric function of KCl:Cu through a sum-over-states formalism and broke it down into different band contributions by partially making an iterated cumulative sum (ICS) of selected valence and conduction bands. Consequently, we identified those interband transitions that give rise to the absorption peaks due to the Cu+ ion. These transitions involve valence and conduction bands formed by the Cu-3d and Cu-4s electronic states.

Structural chemistry of fluoride and mixed-ligand fluoride complexes of gallium(III)

This article covers the structural chemistry of fluoride and mixed-ligand fluoride complexes of gallium(III), discusses more than 140 known crystal structures of anionic fluoride and mixed-ligand fluoride complexes and continues the discussion initiated in previous reviews dedicated to the stereochemistry and structural chemistry of group III–V metals fluoride complexes. Most of these structures have been established by single-crystal X-ray diffraction techniques, but some were characterized by powder X-ray diffraction methods. This paper offers a discussion of the geometry of gallium and outer sphere cation coordination polyhedra, the association of gallium atoms in dimer and polymer formations, types of cation-anion interactions, and their contributions in actual three-dimensional crystal structures. The structural information has been compiled in a single table containing phase compositions and the corresponding standard crystallographic data (such as crystal system, space group, unit cell parameters, number of formula units per cell [Z], reliability factors [R1], Ga-F, and Ga-O bond lengths).