Revisiting the Zintl‒Klemm Concept for ALn2Ag3Te5-Type Alkaline-Metal (A) Lanthanide (Ln) Silver Tellurides

Katharina Eickmeier,Simon Steinberg,Kai Fries,Fabian Gladisch,Richard Dronskowski

doi:10.3390/cryst10030184

Katharina Eickmeier, Simon Steinberg + Show 3 more

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https://doi.org/10.3390/cryst10030184

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Abstract

Understanding the bonding nature of solids is decisive, as knowledge of the bonding situation for any given material provides valuable information about its structural preferences and physical properties. Although solid-state tellurides are at the forefront of several fields of research, the electronic structures, particularly their nature of bonding, are typically understood by applying the Zintl‒Klemm concept. However, certain tellurides comprise ionic as well as strong (polar) mixed-metal bonds, in obvious contrast to the full valence-electron transfers expected by Zintl‒Klemm’s reasoning. How are the valence-electrons really distributed in tellurides containing ionic as well as mixed-metal bonds? To answer this question, we carried out bonding and Mulliken as well as Löwdin population analyses for the series of ALn2Ag3Te5-type tellurides (A = alkaline-metal; Ln = lanthanide). In addition to the bonding analyses, we provide a brief description of the crystal structure of this particular type of telluride, using the examples of RbLn2Ag3Te5 (Ln = Ho, Er) and CsLn2Ag3Te5 (Ln = La, Ce), which have been determined for the first time.

Highlights

In the quest for task-specific solid-state materials, computational materials design is of great relevance, because these density-functional-theory-based approaches provide valuable information regarding thermodynamic quantities and, the physical properties of materials [1]
All tellurides were obtained from reactions of the corresponding rare-earth elements, silver and tellurium in the presence of the respective alkaline-metal chlorides that were employed as reactive fluxes [22]
A phase analysis was accomplished based on the powder X-ray diffraction patterns collected for the samples, and it revealed that the tellurides were obtained in considerable yields; yet, all tellurides were accompanied by by-products that were binary lanthanide tellurides, Ag2 Te, CsAg5 Te3, and an unknown phase

Summary

Introduction

In the quest for task-specific solid-state materials, computational materials design is of great relevance, because these density-functional-theory-based approaches provide valuable information regarding thermodynamic quantities and, the physical properties of materials [1]. The bond energy contributes to the total electronic (ground state) energy, providing conclusive hints to the structural preferences of materials [3,4], while the bonding characteristics of the states near the Fermi level of a given material influence its physical properties. The latter circumstance becomes fully apparent regarding the Fermi level characteristics of certain chalcogenide superconductors [5,6], the magnetic ground state of transition-metals [7], and the optical as well as the electric properties of phase-change materials [8,9], to name but a few.

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