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Falk M, Röhr C. Stacking polytypes of mixed alkali gallides/indides A
1–2(Ga/In)3 (A=K, Rb, Cs): synthesis, crystal chemistry and chemical bonding. Z KRIST-CRYST MATER 2019. [DOI: 10.1515/zkri-2019-0031] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
The Ga/In phase width (y) and the distribution of the two triels within the polyanions of known binary (x = 1, 2) and new ternary ‘intermediate’ (x = 1–2) alkali trielides Ax
(Ga1−
y
In
y
)3 (A = K, Rb, Cs) was investigated in a synthetic (slow cooling of the melts of the three elements), crystallographic (X-ray single crystal) and bond theoretical (FP-LAPW DFT bandstructure calculation) study. The Cs2In3-type structure (x = 2, series A, tetragonal, I 4/mmm) exhibits layers of four-connected closo octahedra [M
6]4−. Ternary K compounds of this type were yielded within a large range (y = 0–0.87), whereas isotypic Rb/Cs trielides exist only at higher In contents (>52/69%). Geometric criteria determine not only the Ga/In stability ranges but also the occurrence of a commensurate superstructure at approx. 33% In (K2Ga2.17In0.83: P 42/ncm, a = 879.83(4), c = 1557.66(10) pm, R 1 = 0.0887), in which the octahedra are slightly tilted against the layers. Cesium compounds of the RbGa3-type structure (x = 1, C, tetragonal, I 4̅m2), which exhibits a 3D network of all-exo bonded closo dodecahedra [M
8]2− and four-bonded M
− anions, are stable throughout the whole substitutional range CsGa3–CsIn3. The maximum possible In content increases with increasing size of A
+ (Cs: 100%, Rb: 30%, K: 8% In). The similarities between these two tetragonal structures are consistent with the occurrence of two new structure types of ‘intermediate’ compounds A
7
M
15 (x = 1.4, 1
B/2
B), which differ in the stacking sequences of double layers of novel six-fold exo-bonded pentagonal bipyramidal closo clusters [M
7]3− connected via four-bonded M
− (e.g. 1
B: Cs7Ga8.4In6.6, P 4̅m2, a = 656.23(3), c = 1616.0(1) pm, R 1 = 0.0742; 2
B: Rb7Ga8.1In6.9, P 42/nmc, a = 665.64(2), c = 3140.9(2) pm, R 1 = 0.0720). The Rb/Cs compounds of these types are only stable in a limited Ga/In region and with a distinct Ga/In distribution within the [M
7] clusters. According to the close relation between the structures A, B and C, the structure family is characterised by the occurrence of stacking faults and diffuse scattering, indicating the existence of further members of this series. The new compound Cs5Ga3.1In5.9 (x = 1.667, P 4̅m2, a = 654.62(2), c = 3281.5(2) pm, R 1 = 0.1005) is a reasonably periodically ordered stacking variant containing layers A and double layers B in parallel.
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Affiliation(s)
- Martha Falk
- Institut für Anorganische und Analytische Chemie , Universität Freiburg , Albertstr. 21 , D-79104 Freiburg , Germany
| | - Caroline Röhr
- Institut für Anorganische und Analytische Chemie , Universität Freiburg , Albertstr. 21 , D-79104 Freiburg , Germany
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Corbett JD. Exploratory Synthesis: The Fascinating and Diverse Chemistry of Polar Intermetallic Phases†This article is based on J. D. Corbett’s address upon receipt of the 2008 American Chemical Society’s F. Albert Cotton Award in Synthetic Inorganic Chemistry sponsored by the F. Albert Cotton Endowment Fund. Inorg Chem 2009; 49:13-28. [DOI: 10.1021/ic901305g] [Citation(s) in RCA: 112] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- John D. Corbett
- Department of Chemistry and Ames Laboratory, Iowa State University, Ames, Iowa 50011
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