Abstract
Averievite-type compounds with the general formula (MX)[Cu5O2(TO4)], where M = alkali metal, X = halogen and T = P, V, have been synthesized by crystallization from gases and structurally characterized for six different compositions: 1 (M = Cs; X = Cl; T = P), 2 (M = Cs; X = Cl; T = V), 3 (M = Rb; X = Cl; T = P), 4 (M = K; X = Br; T = P), 5 (M = K; X = Cl; T = P) and 6 (M = Cu; X = Cl; T = V). The crystal structures of the compounds are based upon the same structural unit, the layer consisting of a kagome lattice of Cu2+ ions and are composed from corner-sharing (OCu4) anion-centered tetrahedra. Each tetrahedron shares common corners with three neighboring tetrahedra, forming hexagonal rings, linked into the two-dimensional [O2Cu5]6+ sheets parallel to (001). The layers are interlinked by (T5+O4) tetrahedra (T5+ = V, P) attached to the bases of the oxocentered tetrahedra in a “face-to-face” manner. The resulting electroneutral 3D framework {[O2Cu5](T5+O4)2}0 possesses channels occupied by monovalent metal cations M+ and halide ions X−. The halide ions are located at the centers of the hexagonal rings of the kagome nets, whereas the metal cations are in the interlayer space. There are at least four different structure types of the averievite-type compounds: the P-3m1 archetype, the 2 × 2 × 1 superstructure with the P-3 space group, the monoclinically distorted 1 × 1 × 2 superstructure with the C2/c symmetry and the low-temperature P21/c superstructure with a doubled unit cell relative to the high-temperature archetype. The formation of a particular structure type is controlled by the interplay of the chemical composition and temperature. Changing the chemical composition may lead to modification of the structure type, which opens up the possibility to tune the geometrical parameters of the kagome net of Cu2+ ions.
Highlights
Mineralogical information provides an important resource for the design of novel materials with a unique structural architecture and physical properties [1,2,3]
The halide ions are located at the centers of the hexagonal rings of the kagome nets, whereas the metal cations are in the interlayer space
The crystal structures of the averievite-type compounds are based upon the same structural unit—the layer consisting of kagome lattice of Cu2+ ions
Summary
Mineralogical information provides an important resource for the design of novel materials with a unique structural architecture and physical properties [1,2,3]. Of particular interest are minerals containing transition metal cations such as Cu2+ that form various cation arrays with interesting magnetic behavior. The kagome lattice consisting of cornersharing Cu3 triangles forming a 2D net with regular hexagonal rings is probably the most famous example—such an array is geometrically frustrated, and this feature is responsible for the spin liquid behavior first demonstrated for synthetic herbertsmithite and later observed for other synthetic mineral analogues [4,5,6,7,8,9,10,11]. In order to exhibit a spin liquid property, the kagome array should possess an ideal trigonal (or hexagonal) symmetry, which is absent in most minerals with the kagome arrangement of Cu2+ magnetic ions. A interesting class of fumarolic Cu minerals is those containing ”additional” oxygen atoms, i.e., atoms that do not participate in strongly bonded “acid residues” (such as sulfate, selenate, arsenate, chlorides, fluorides, etc.) and form anion-centered (OCu4) tetrahedra [16]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
