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Phase change materials (PCMs), which bear a strong relationship with pnictogens (group V or 15) and chalcogens (group VI or 16), are mostly chalcogens related to AIVBVI and A V2 B VI3 families. The exceptional properties and technological applications of PCMs have sparked interest in the nature of the unconventional chemical bonding present in the crystalline phases of PCMs, which has been reported as resonant, hypervalent, electron-rich multicenter, three-center-four-electron, and metavalent bonding along the last seventy years. This unconventional bond is also expected to occur at high pressure in most pnictogens, chalcogens, and AIVBVI and A V2 B VI3 compounds that are not PCMs at room pressure. These compounds are characterized at room pressure by a mixture of primary covalent ppσ-bonds and secondary bonds in which the lone electron pairs (LEPs) are involved. In this work, we provide evidence of the existence of an unconventional bonding (similar to that of PCMs) in the highpressure phases of pnictogens and chalcogens using theoretical simulations. We also unravel the mechanism of its formation and how it depends on the type of LEP present in secondary bonds. Moreover, we show that the unconventional bond of PCMs is the electron-deficient multicenter bond. This comprehensive understanding of chemical bonding in pnictogens and chalcogens, which can be extrapolated to advanced materials, such as PCMs, will play a crucial role in explaining the structure and properties of advanced materials as well as in enhancing their applications. [ABSTRACT FROM AUTHOR]

The effect of pressure on the structural, vibrational, and optical properties of lead thiogallate, PbGa2S4, crystallizing under room conditions in the orthorhombic EuGa2S4-type structure (space group Fddd), 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 ab initio calculations, but also to the related compounds α′-Ga2S3, CdGa2S4, and HgGa2S4. Evidence of a partially reversible pressure-induced decomposition of PbGa2S4 into a mixture of Pb6Ga10S21 and Ga2S3 above 15 GPa is reported. Thus, our measurements and calculations show a route for the high-pressure synthesis of Pb6Ga10S21, which is isostructural to the stable Pb6In10S21 compound at room pressure. [ABSTRACT FROM AUTHOR]

A new ternary lithium zinc germanide, Li13.83Zn1.17(2)Ge4, was synthesized by a high‐temperature solid state reaction of the respective elements. The crystal structure was determined by single‐crystal X‐ray diffraction methods. The new phase crystallizes in the body‐centered cubic space group I4‾ 3d (no. 220) with unit cell parameter of 10.695(1) Å. The crystal structure refinements show that the parent Li15Ge4 structure is stabilized as Li15−xZnxGe4 (x≈1) via random substitution of Li atoms by the one‐electron‐richer atoms of the element Zn, by virtue of which the number of valence electrons increases, leading to a more electronically stable system. The substitution effects in the parent Li15Ge4 structure were investigated through both theory and experiment, which confirm that the Zn atoms in this structure prefer to occupy only one of the two available crystallographic sites for Li. The preferred substitution pattern established from experimental results is supported by DFT electronic structure calculations, which also explore the subtleties of the chemical bonding and the electronic properties of the title compounds. [ABSTRACT FROM AUTHOR]

A new ternary lithium zinc germanide, Li13.83Zn1.17(2)Ge4, was synthesized by a high‐temperature solid state reaction of the respective elements. The crystal structure was determined by single‐crystal X‐ray diffraction methods. The new phase crystallizes in the body‐centered cubic space group I4‾ 3d (no. 220) with unit cell parameter of 10.695(1) Å. The crystal structure refinements show that the parent Li15Ge4 structure is stabilized as Li15−xZnxGe4 (x≈1) via random substitution of Li atoms by the one‐electron‐richer atoms of the element Zn, by virtue of which the number of valence electrons increases, leading to a more electronically stable system. The substitution effects in the parent Li15Ge4 structure were investigated through both theory and experiment, which confirm that the Zn atoms in this structure prefer to occupy only one of the two available crystallographic sites for Li. The preferred substitution pattern established from experimental results is supported by DFT electronic structure calculations, which also explore the subtleties of the chemical bonding and the electronic properties of the title compounds. [ABSTRACT FROM AUTHOR]

In this paper, we discuss the synthesis and the structural characterization of the new ternary compound Sr7Li6Sn12 and its six quaternary derivatives, where alkaline earth metals (Ca, Mg, Ba) and the rare earth metal Eu are substituted, yielding crystalline phases of monoclinic or orthorhombic symmetry. The title compounds were synthesized via high‐temperature solid‐state reactions of the corresponding elements. The crystal structures were determined by single‐crystal X‐ray diffraction methods. The (Sr,Ca)7Li6Sn12 and Eu7(Mg,Li)6Sn12 phases represent a new structure type (space group P2/m, No. 10) while Sr7Li6Sn12 and the rest of the title phases crystallize in the orthorhombic base‐centered space group Cmmm (No. 65) which is similar to the Eu7Li8–xSn10+x (x ≈ 2.0) phase with the Ce7Li8Ge10 structure type (Pearson code oC50). Careful examination of the resulting structures shows intricate disordering between Li and Sn atoms, which is governed by the total number of valence electrons. The discussion of experimental results is also supported by DFT electronic structure calculations. [ABSTRACT FROM AUTHOR]

Cover Feature: Experimental and Theoretical Study on the Substitution Patterns in Lithium Germanides: The Case of Li15Ge4 vs Li14ZnGe4 (Eur. J. Inorg. Germanides, Lithium, Solid-state synthesis, Structure elucidation, Zintl phases Keywords: Germanides; Lithium; Solid-state synthesis; Structure elucidation; Zintl phases EN Germanides Lithium Solid-state synthesis Structure elucidation Zintl phases 1 1 1 02/07/22 20220208 NES 220208 B The Cover Feature b shows the synthesis of Li SB 14 sb ZnGe SB 4 sb by substitution of Li by Zn within the parent Li SB 15 sb Ge SB 4 sb binary phase. [Extracted from the article]

The effect of pressure on the structural, vibrational, and optical properties of lead thiogallate, PbGa 2 S 4 , crystallizing under room conditions in the orthorhombic EuGa 2 S 4 -type structure (space group Fddd ), 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 ab initio calculations, but also to the related compounds α'-Ga 2 S 3 , CdGa 2 S 4 , and HgGa 2 S 4 . Evidence of a partially reversible pressure-induced decomposition of PbGa 2 S 4 into a mixture of Pb 6 Ga 10 S 21 and Ga 2 S 3 above 15 GPa is reported. Thus, our measurements and calculations show a route for the high-pressure synthesis of Pb 6 Ga 10 S 21 , which is isostructural to the stable Pb 6 In 10 S 21 compound at room pressure., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The characterization of bonding interactions in molecules and materials is one of the major applications of quantum mechanical calculations. Numerous schemes have been devised to identify and visualize chemical bonds, including the electron localization function, quantum theory of atoms in molecules, and natural bond orbital analysis, whereas the energetics of bond formation are generally analyzed in qualitative terms through various forms of energy partitioning schemes. In this Article, we illustrate how the chemical pressure (CP) approach recently developed for analyzing atomic size effects in solid state compounds provides a basis for merging these two approaches, in which bonds are revealed through the forces of attraction and repulsion acting between the atoms. Using a series of model systems that include simple molecules (H 2 , CO 2 , and S 8 ), extended structures (graphene and diamond), and systems exhibiting intermolecular interactions (ice and graphite), as well as simple representatives of metallic and ionic bonding (Na and NaH, respectively), we show how CP maps can differentiate a range of bonding phenomena. The approach also allows for the partitioning of the potential and kinetic contributions to the interatomic interactions, yielding schemes that capture the physical model for the chemical bond offered by Ruedenberg and co-workers.