Anion Ordering in Bichalcogenides

Abstract

This review contains recent developments and new insights in the research on inorganic, crystalline compounds with two different chalcogenide ions (bichalcogenides). Anion ordering is used as a parameter to form structural dimensionalities as well as local-and global-electric polarities. The reason for the electric polarity is that, in the heterogeneous bichalcogenide lattice, the individual bond-lengths between cations and anions are different from those in a homogeneous anion lattice. It is also shown that heteroleptic tetrahedral and octahedral coordinations offer a multitude of new crystal fields and coordinations for involved cations. This coordination diversity in bichalcogenides seems to be one way to surpass electro-chemical redox potentials Further, the potential of the anion lattice is discussed as a parameter for future materials design.

Mixed Anion Semiconductor In8S2.82Te6.18(Te2)3

“…Though limited to date, the synthesis of mixed chalcogenides has been demonstrated with the heteroanionic compounds crystallizing in either the same structure type as the parent compound or in a new structure type. , The differences in electronegativity and size are sufficient to produce compounds with anions on distinct crystallographic sites (as opposed to solid solutions or anion substitutions, where the anions are positionally disordered). , In fact, it has been observed that a 10% difference in anionic size stabilizes an ordered structure instead of resulting in a solid solution. , It has also been suggested that the closer the Q : Q ′ ratio is to unity, the higher the dimensionality of the structure; for example, a 1:1 ratio often yields a three-dimensional (3D) lattice, 2:1 a two-dimensional (2D) lattice, and 6:1 a zero-dimensional (0D) lattice . When the anions order, they may remain in the parent structure type or crystallize in a different structure type.…”

“…Heteroleptic bonding can occur when the metal cations are amphoteric (e.g., classified as borderline hard or soft Lewis acids), the anionic species are similar in size (e.g., N 3– , O 2– , S 2– , F – ), or the anions are sufficiently small that they can coordinate around the same metal cation. This, in turn, may generate irregularities in bonding, such as the lengths of metal–anion bonds, which influence local polarization and crystal fields. , On the whole, the long-range ordering of either of these bonding types yields global changes in the material properties. , …”

Flux Crystal Growth, Structure, and Optical Properties of the New Germanium Oxysulfide La4(GeS2O2)3

“…[1][2][3] Mixed-anion structures containing oxide ions and different period 3-5 anions, such as oxide-sulfide and oxide-arsenide combinations, exclusively exhibit long-range anion ordering, particularly anion segregation in two dimensional (2D) layers. [4][5][6][7] These anion segregations can be explained by the hard-soft acid-base (HSAB) theory, 8 in which highly electropositive/polarizable cations prefer to bond with highly electronegative/polarizable anions. However, exceptions to the HSAB theory, namely higher dimensional anion distributions, exist when differences in electronegativity (or polarizability) are small or when the concentration of a given anion is high compared to that of the other.…”

“…Mixed-anion compounds, in which two or more anionic species are incorporated into one crystal structure, have provided a playground for solid-state chemists to explore unique properties. Differences in the essential characteristics of anions, i.e., ionic radius, electronegativity, oxidation state, and polarizability, often lead to short- or long-range ordering of the anions, resulting in the formation of new anion sublattices and building blocks. − Mixed-anion structures containing oxide ions and different period 3–5 anions, such as oxide-sulfide and oxide-arsenide combinations, exclusively exhibit long-range anion ordering, particularly anion segregation in two-dimensional (2D) layers. − These anion segregations can be explained by the hard–soft acid–base (HSAB) theory, in which highly electropositive/polarizable cations prefer to bond with highly electronegative/polarizable anions. However, exceptions to the HSAB theory, namely, higher dimensional anion distributions, exist when differences in electronegativity (or polarizability) are small or when the concentration of a given anion is high compared to that of the other.…”

Synthesis, Crystal Structure, and Optical Characterization of the Sulfide Chloride Oxide CsBa6V4S12ClO4 with a Near-Infrared Fluorescence

“…The latter offers rare and novel physical situations and occurs frequently in bichalcogenides, i.e. in a lattice combined of two different chalcogenide anions . Of these, the sulfide-oxides are by far the most investigated, and even their tetrahedral heteroleptic coordinations have extensive flexibility.…”