Revealing the Bonding Nature in an ALnZnTe3-Type Alkaline-Metal (A) Lanthanide (Ln) Zinc Telluride by Means of Experimental and Quantum-Chemical Techniques

Exploring the Interdependence between Electronically Unfavorable Situations and Pressure in a Chalcogenide Superconductor

The development of solids with the requested chemical and physical properties requires a thorough understanding of their electronic structures, as proper knowledge of the electronic structure of a given solid provides invaluable information regarding its properties. In this context, recent research on two competing sorts of electronic instabilities in chalcogenide superconductors stimulated us to explore the interdependence between these instabilities and another aspect, pressure, which was previously shown to influence the presence of a superconducting state in diverse solids. To accomplish our goal, we carried out pressure-dependent examinations of the electronic structures of two tellurides, YTe and YTe0.97, which were inspected as prototypes in our explorations based on quantum-chemical means. In addition to our pressure-dependent explorations of the electronic structures, we also performed chemical bonding analyses to reveal the subtle interplay between pressure and two sorts of electronically unfavorable situations.

Examination of a Structural Preference in Quaternary Alkali-Metal (A) Rare-Earth (R) Copper Tellurides by Combining Experimental and Quantum-chemical Means

In the quest for materials addressing the grand challenges of the future, there is a critical need for a broad understanding of their electronic structures because the knowledge of the electronic structure of a given solid allows us to recognize its structural preferences and to rationalize its properties. As previous research on quaternary chalcogenides containing active metals (a group-I- or -II-element), early transition-metals, and late transition-metals indicated that such materials could pose as alluring systems in the developments of thermoelectrics, our impetus was stimulated to probe the suitability of tellurides belonging to the prolific A₃R₄Cu₅Te₁₀-family. In doing so, we first used quantum-chemical techniques to explore the electronic and vibrational properties of representatives crystallizing with different A₃R₄Cu₅Te₁₀ structure types. The outcome of these explorations indicated that the aspects that control the formation of a given type of A₃R₄Cu₅Te₁₀ structure are rather subtle so that transitions between different types of A₃R₄Cu₅Te₁₀ structures could be induced by manipulating the ambient conditions. To probe this prediction, we explored the thermal behavior for the example of one quaternary telluride, that is, Rb₃Er₄Cu₅Te₁₀, and thereby identified a new type of A₃R₄Cu₅Te₁₀ structure. Because understanding the structural features of the A₃R₄Cu₅Te₁₀ family plays an important role in the analyses of the aforementioned explorations, we also present an overview about the structural features and the members of this class of quaternary tellurides. In this connection, we also provide a structural report of four tellurides, that is, K₃Tb₄Cu₅Te₁₀ and Rb₃R₄Cu₅Te₁₀ (R = Tb, Dy, Ho), which have been obtained from high-temperature solid-state reactions for the very first time.

Exploring the frontier between polar intermetallics and Zintl phases for the examples of the prolific ALnTnTe3-type alkali metal (A) lanthanide (Ln) late transition metal (Tn) tellurides

Understanding electronic structures is important in order to interpret and to design the chemical and physical properties of solid-state materials. Among those materials, tellurides have attracted an enormous interest, because several representatives of this family are at the cutting edge of basic research and technologies. Despite this relevance of tellurides with regard to the design of materials, the interpretations of their electronic structures have remained challenging to date. For instance, most recent research on tellurides, which primarily comprise post-transition elements, revealed a remarkable electronic state, while the distribution of the valence electrons in tellurides comprising group-I/II elements could be related to the structural features by applying the Zintl-Klemm-Busmann concept. In the cases of tellurides containing transition metals the applications of the aforementioned idea should be handled with care, as such tellurides typically show characteristics of polar intermetallics rather than Zintl phases. And yet, how may the electronic structure look like for a telluride that consists of a transition metal behaving like a p metal? To answer this question, we examined the electronic structure for the quaternary RbTbCdTe3 and provide a brief report on the crystal structures of the isostructural compounds RbErZnTe3 and RbTbCdTe3, whose crystal structures have been determined by means of X-ray diffraction experiments for the very first time.

Bonding diversity in rock salt-type tellurides: examining the interdependence between chemical bonding and materials properties

Future technologies are in need of solid-state materials showing the desired chemical and physical properties, and designing such materials requires a proper understanding of their electronic structures. In this context, recent research on chalcogenides, which were classified as 'incipient metals' and included phase-change data storage materials as well as thermoelectrics, revealed a remarkable electronic behavior and possible state (dubbed 'metavalency') proposed for the frontier between entire electron localization and delocalization. Because the members of the family of the polar intermetallics vary widely in their properties as well as electronic structures, one may wonder if the aforementioned electronic characteristics are also achieved for certain polar intermetallics. To answer this question, we have employed quantum-chemical tools to examine the electronic structures of the rock salt-type YTe and SnTe belonging to the families of the polar intermetallics and incipient metals, respectively. To justify these classifications and argue as to why an application of the Zintl-Klemm concept (frequently employed to relate the structural features of tellurides to their electronic structures) could be misleading for YTe and SnTe, the electronic structures of YTe and SnTe were first compared to that of the rock salt-type SrTe. In addition, we carried out a Gedankenexperiment by subsequently modifying the chemical composition from YTe to SnTe, and, by doing so, we shed new light on the interdependence between chemical bonding and materials properties. Gradual changes in the former do not necessarily translate into the latter which may undergo discontinuous modifications.