Structural Uniqueness of the [Nb(As₅)₂]^5– Cluster in the Zintl Phase Cs₅NbAs₁₀

Abstract

The structure of the novel Zintl phase, Cs 5 NbAs 10 , is reported for the first time. This compound crystallizes in the monoclinic P2 1 /c space group (no. 14) with eight formula units per cell. The structure represents a unique atomic arrangement, constituting a new structure type with Wyckoff sequence e32. The most important structural element is the unprecedented [Nb(As 5 ) 2 ] 5− cluster anion, formed by a Nb atom enclosed between two As 5 rings. These nonaromatic cyclic species, formally [As 5 ] 5− , adopt an envelope conformation similar to that of cyclopentane. To date, it is only the second example of an [As 5 ] 5− ring with this conformation, reported in an inorganic solidstate compound. The bonding characteristics of the [Nb(As 5 ) 2 ] 5− cluster and the [As 5 ] 5− rings are thoroughly investigated using first-principles methods and discussed. Electronic band structure calculations on Cs 5 NbAs 10 suggest that this compound is a semiconductor with an estimated band gap of ca. 1.4 eV.

On the Effects of Aliovalent Substitutions in Thermoelectric Zintl Pnictides. Varied Polyanionic Dimensionality and Complex Structural Transformations─The Case of Sr3ZnP3 vs Sr3AlxZn1–xP3

“…The calculated −ICOHP value of ca. 2.61 eV/bond indicates strong covalent interaction and was already observed in several Zintl phases with homoatomic Pn–Pn bonding. ,− …”