Abstract

Understanding the nature of bonding in solid-state materials is of great interest for their designs, because the bonding nature influences the structural preferences and chemical as well as physical properties of solids. In the cases of tellurides, the distributions of valence-electrons are typically described by applying the Zintl−Klemm concept. Yet, do these Zintl−Klemm treatments provide adequate pictures that help us understanding the bonding nature in tellurides? To answer this question, we followed up with quantum-chemical examinations on the electronic structures and the bonding nature of three alkaline-metal copper tellurides, i.e., NaCu3Te2, K2Cu2Te5, and K2Cu5Te5. In doing so, we accordingly probed the validity of the Zintl−Klemm concept for these ternary tellurides, based on analyses of the respective projected crystal orbital Hamilton populations (−pCOHP) and Mulliken as well as Löwdin charges. Since all of the inspected tellurides are expected to comprise Cu−Cu interactions, we also paid particular attention to the possible presence of closed-shell interactions.

Highlights

  • Tellurides, which are compounds [1,2] that are considered to comprise of at least one tellurium atom in a reduced state relative to its elemental form, have attracted an enormous interest among chemists, physicists, and engineers

  • To explore the bonding nature of Cu−Cu interactions in tellurides, which are expected to comprise such closed-shell interactions, we carried out bonding analyses for the ternary NaCu3 Te2, K2 Cu2 Te5, and K2 Cu5 Te5, whose crystal structures have been determined by previous experimental research [33,34,35]

  • The crystal structure of NaCu3 Te2, which has recently been subject to explorations on topological semi-metals [50,51], (Figure 2) comprises three independent copper positions: the copper atoms corresponding to two of these sites (Cu1 and Cu2) reside in the centers of tellurium tetrahedra, while the Cu3 atoms occupy octahedral voids enclosed by the tellurium atoms; the Cu3 atoms are displaced from the centers of these octahedral voids such that each Cu3 atom rather assembles a trigonal pyramid with three tellurium atoms of one of the faces of each octahedron

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Summary

Introduction

Tellurides, which are compounds [1,2] that are considered to comprise of at least one tellurium atom in a reduced state relative to its elemental form, have attracted an enormous interest among chemists, physicists, and engineers. In the spirit of and contained transition-metals cases in light of hypervalency [21,22] In this the formalism, the interactions between tellurium atoms and early as well as late. Inthan viewionic of the outcome of interactions should(polar) be depicted as strong (polar) mixed-metal-like bonds rather bonds In view these quantum-chemical explorations and the aforementioned reports on ionic early-TM−Te interacof the outcome of these quantum-chemical explorations and the aforementioned reports on ionic tions, it was concluded thatitthe distributions as suggested by the Zintl−Klemm treatearly-TM−Te interactions, wasvalence-electron concluded that the valence-electron distributions as suggested by the ments could betreatments misleading and,behence, shouldand, be regarded with be concern. These tellurides, which are presented as an outcome of our explorations in the present contribution

Computational Details
Results and Discussion
Conclusions

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