Fermi-Level Characteristics of Potential Chalcogenide Superconductors

Abstract

Quantum chemical high-throughput screenings of compound libraries for the identifications of materials with the desired properties have emerged as beneficial tools to accelerate the discoveries of compounds of interest. The quantum chemical high-throughput screenings of compound libraries require the definitions of reliable descriptors enabling relationships between the observed physical properties and the computed electronic structures. The desire to enhance the discoveries of materials showing electronic instabilities which are related to possible metalto-superconductor transitions stimulated our impetus to probe the feasibility of a descriptor for the identifications of materials with the aforementioned electronic instabilities in the forms of flat bands crossing the Fermi levels. To evaluate the reliability of the projected descriptor based on the f lat band/steep band scenario for superconductors, we inspected the characteristics of the electronic band structures near the Fermi levels for a series of chalcogenide superconductors, whose electronic structures were computed and analyzed by means of first-principles-based highthroughput techniques. Article pubs.acs.org/cm

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

“…In accordance with previous research [31] on cesium-containing polar intermetallics, such small −IpCOHP/bond values point to less populated Cs−Te states due to the electron-donor character of Cs, while the Ce−Te and Ag−Te interactions may be regarded as (polar) mixed-metal bonds. This outcome is also in contrast to a full electron transfer according to Zintl-Klemm, proposing a valence-electron distribution of (Cs + )(Ce 3+ ) 2 (Ag + ) 3 (Te 2− ) 5 . The absence of a full transfer of valence-electrons, as expected by Zintl-Klemm, is also given by the Mulliken and Löwdin charges (Figure 3).…”

“…The crystal structures of the ALn 2 Ag 3 Te 5 -type tellurides (see Figure 3) are composed of tunnels, which are constructed by tellurium atoms and encompass the alkaline-metal, rare-earth metal, and silver atoms. The alkaline-metal atoms occupy the centers of bicapped trigonal tellurium prisms, whose triangular bases are condensed to 1 ∞ All silver atoms occupy the centers of the tellurium tetrahedra, which are condensed to linear 1 ∞ [Ag@Te 4 chains, but there are two different types of 1 ∞ [Ag@Te 4 chains in the crystal structure of the ALn 2 Ag 3 Te 5 -type tellurides (see Figure 3 5 . Indeed, such a Zintl-Klemm picture is oversimplistic because more recent research [18] on the nature of bonding for this particular type of telluride revealed strong mixed-metal interactions for the Ln−Te and Ag−Te contacts.…”

“…Namely, the bond energy evidently 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. For instance, 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.…”

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

“…Because of their remarkable chemical and physical properties, chalcogenides, which comprise at least one chalcogen atom in a reduced oxidation state relative to its elemental form, have gained great interest in the quest for materials that are exploited in technologies to address future challenges [1]. Among the family of chalcogenides, tellurides are of particular interest, because several tellurides are at the forefront of technologies and basic research, including explorative efforts in charge-density-waves [2][3][4], phase-change data storage devices [5,6], thermoelectrics [7,8], and topological insulators [9], to name a few. In light of such a relevance of tellurides for basic research, it is also mandatory to determine and understand their electronic structures, because the knowledge of the electronic structure for a given material provides valuable information regarding its chemical and physical properties [10].…”

Probing the Validity of the Zintl−Klemm Concept for Alkaline-Metal Copper Tellurides by Means of Quantum-Chemical Techniques

“…Namely, the bond energy has a significant contribution to the total (electronic ground state) energy [11,12], and the bonding characteristics at the Fermi level of a given material provide valuable hints accounting for its properties. The former aspect is extremely relevant for the evaluations of the total energies in order to justify and predict the formations of solid-state materials [13,14], while the bonding nature at the Fermi level, for instance, accounts for the presence of superconducting states in certain chalcogenides [15,16], magnetic ground states in transition-metals [17], or occurrence of vacancies 2 of 12 in phase-change materials [18]. In the cases of the tellurides, the valence-electron distributions are typically determined by applying the Zintl−Klemm concept, which has originally [19,20] been introduced to understand correlations between structural features and valence-electron distributions in intermetallics composed of main group elements.…”