K2In12Se19, a complex new structure type based on icosahedral units of Se2-

Citation
M. Schlosser et al., K2In12Se19, a complex new structure type based on icosahedral units of Se2-, EUR J INORG, (9), 2001, pp. 2241-2247
Citations number
24
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Inorganic & Nuclear Chemistry
Journal title
EUROPEAN JOURNAL OF INORGANIC CHEMISTRY
ISSN journal
1434-1948 → ACNP
Issue
9
Year of publication
2001
Pages
2241 - 2247
Database
ISI
SICI code
1434-1948(200109):9<2241:KACNST>2.0.ZU;2-A
Abstract
K2In12Se19 is a new ternary chalcogenide in the system K2Se-In2Se3 (m.p. 99 7 K; colour: dark red) with the two components in a molar ratio of 1:6. Thi s unusual solid shows a temperature-dependent order-disorder transition ori ginating mainly from a dynamical disorder of In3+ at elevated temperatures. The average structure of the dynamically disordered phase at 673 K was ana lysed by means of high-temperature single-crystal X-ray data [a = 1393.18(5 ) pm, c = 1772.26(9) pm, Z = 3, R (3) over bar, hexagonal setting]. The mos t prominent feature of the complex solid is a partial structure of slightly distorted icosahedra formed by Set (central atom), Se3, and Se4. The topol ogical arrangement of the icosahedra corresponds to a cubic close packing. A further independent partial structure enveloping the icosahedra is build up by Set. The latter form large distorted polyhedra intermediate between i cosahedra and cuboctahedra. In1, In2, and In3 occupy tetrahedral holes insi de (In2) and outside the icosahedra (In1 and In3), whereas K is located in distorted octahedral holes. In2 and In3 are located in neighboured face-sha ring tetrahedra showing an approximate 50% occupancy. They are alternativel y occupied in the sense of a dynamical disorder ("average structure"). In1 and K are not affected directly by the disorder. Structural relations betwe en K2In12Se19 and an earlier published unusual quaternary indium chalcogeni de are discussed.