Rethinking polyiodides: the role of electron-deficient multicenter bonds.

Despite a bicentennial history, the interest in polyiodides and related systems still flourishes. The chemical puzzle provided by the intricate nature of chemical bonding in these polyanions remains challenging these days. The advent of the halogen bond and the spreading interest in supramolecular interactions of halogen-based systems promoted further recent interest.

Electron-Deficient Multicenter Bonding in Phase Change Materials: A Chance for Reconciliation.

In the last few years, a controversy has been raised regarding the nature of the chemical bonding present in phase change materials (PCMs), many of which are minerals such as galena (PbS), clausthalite (PbSe), and altaite (PbTe). Two opposite bonding models have claimed to be able to explain the extraordinary properties of PCMs in the last decade: the hypervalent (electron-rich multicenter) bonding model and the metavalent (electron-deficient) bonding model. In this context, a third bonding model, the electron-deficient multicenter bonding model, has been recently added.

Size-Dependent High-Pressure Behavior of Pure and Eu-Doped YO Nanoparticles: Insights from Experimental and Theoretical Investigations.

We report a joint high-pressure experimental and theoretical study of the structural, vibrational, and photoluminescent properties of pure and Eu-doped cubic YO nanoparticles with two very different average particle sizes. We compare the results of synchrotron X-ray diffraction, Raman scattering, and photoluminescence measurements in nanoparticles with ab initio density-functional simulations in bulk material with the aim to understand the influence of the average particle size on the properties of pure and doped YO nanoparticles under compression. We observe that the high-pressure phase behavior of YO nanoparticles depends on the average particle size, but in a different way to that previously reported.

Electronic, Vibrational, and Structural Properties of the Natural Mineral Ferberite (FeWO): A High-Pressure Study.

This paper reports an experimental high-pressure study of natural mineral ferberite (FeWO) up to 20 GPa using diamond-anvil cells. First-principles calculations have been used to support and complement the results of the experimental techniques. X-ray diffraction patterns show that FeWO crystallizes in the wolframite structure at ambient pressure and is stable over a wide pressure range, as is the case for other wolframite AWO (A = Mg, Mn, Co, Ni, Zn, or Cd) compounds.

Joint experimental and theoretical study of PbGaS under compression.

The effect of pressure on the structural, vibrational, and optical properties of lead thiogallate, PbGaS, crystallizing under room conditions in the orthorhombic EuGaS-type structure (space group ), is investigated. The results from X-ray diffraction, Raman scattering, and optical-absorption measurements at a high pressure beyond 20 GPa are reported and compared not only to calculations, but also to the related compounds α'-GaS, CdGaS, and HgGaS. Evidence of a partially reversible pressure-induced decomposition of PbGaS into a mixture of PbGaS and GaS above 15 GPa is reported.