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The tailored design of solid‐state materials requires a proper understanding of their respective electronic structures. In order to rationalize the relationships between crystal structures and electronic structures in intermetallic compounds, the Zintl‐Klemm concept has been frequently employed. Yet, the frontier between the valence‐electron concentrations (e/a) of the Zintl‐ and the polar intermetallic phases has remained unclear to date. To shed some light on this frontier, we explored the electronic structure of the quaternary compound Rb3Er4Cu5Te10. To this effect, the crystal structure of this telluride, which was obtained as pure phase from high‐temperature reactions, was determined by means of X‐ray diffraction experiments for the very first time. In addition, the magnetic properties of the Rb3Er4Cu5Te10 were also determined in order to explore the erbium 4 f states in more detail. [ABSTRACT FROM AUTHOR]

The bonding nature between chalcogenides and rare‐earth‐elements is typically described as ionic in the spirit of the Zintl‐Klemm formalism; yet, recent efforts showed that lanthanides also act as d‐metals in transition‐metal‐post‐transition‐metal‐element bonding. Hence, how can we describe the bonding nature between chalcogen and europium atoms, which have frequently acted as electron‐donors like group‐I/II‐elements? To answer this question, we prototypically explored the electronic structure of Eu2CuSe3, which was obtained in considerable yields from solid‐state reactions of the pure elements at 600 °C. The crystal structure of Eu2CuSe3 was determined based on X‐ray diffraction experiments and it is composed of diverse types of linear chains of selenium polyhedra enclosing the copper and europium atoms. These chains are condensed into ∞2 [EuCuSe3] layers, which are separated by additional europium atoms. From analyses of the crystal structure and electronic structure of Eu2CuSe3, it is clear that there are two different europium valence states, whose nature controls if europium acts as an electron‐donor like a group‐I/II‐element or as a d‐metal. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The complex metal-rich boride Ti 5- x Fe 1- y Os 6+ x+y B 6 (0 < x , y < 1), crystallizing in a new structure type (space group Cmcm , no. 63), was prepared by arc-melting. The new structure contains both isolated boron atoms and zigzag boron chains (B-B distance of 1.74 Å), a rare combination among metal-rich borides. In addition, the structure also contains Fe-chains running parallel to the B-chains. Unlike in previously reported structures, these Fe-chains are offset from each other and arranged in a triangular manner with intrachain and interchain distances of 2.98 and 6.69 Å, respectively. Density functional theory (DFT) calculations predict preferred ferromagnetic interactions within each chain but only small energy differences for different magnetic interactions between them, suggesting a potentially weak long-range order. This new structure offers the opportunity to study new configurations and interactions of magnetic elements for the design of magnetic materials.