Theoretical predictions of novel potassium chloride phases under pressure

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.

Bonding between electron-deficient atoms: strong Lewis-acid character preserved in X–Y–X (X = B, Al; Y = Be, Mg) bridges

Beryllium bis(diazaborolyl) derivatives and their Mg and Al-containing analogues are stable compounds stabilized through covalent bonds between electron-deficient atoms, and behave as good Lewis acids.

Alkali subhalides: high-pressure stability and interplay between metallic and ionic bonds

The high pressure stability of alkali subhalides is rationalized by means of a thorough chemical bonding analysis.

Structural and electronic properties of alkali metal peroxides at high pressures

Different phase transition mechanisms and structures have been observed for alkali metal peroxides (Li₂O₂, Na₂O₂, K₂O₂, Rb₂O₂) under pressure. Phase transition pressures of the studied compounds closely related to the alkali metal electronegativity.