K{sub 2}Ca{sub 6}Si{sub 4}O{sub 15}-structural and spectroscopical studies on a mixed tetrahedral-octahedral framework

Journal Article · Tue Dec 15 00:00:00 EST 2009 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2009.09.013· OSTI ID:21372418

Arroyabe, E; Kaindl, R; Toebbens, D M ^[1]; Kahlenberg, V ^[1]

---

1. Institute of Mineralogy and Petrography, University of Innsbruck, Innrain 52, A-6020 Innsbruck (Austria)

In the course of an excursion into the system K{sub 2}O-CaO-SiO{sub 2}, single crystalline material of the previously unknown compound K{sub 2}Ca{sub 6}Si{sub 4}O{sub 15} has been obtained. Single crystal X-ray diffraction experiments revealed that the new phase is monoclinic (space group P12/c1) with the following basic crystallographic data: a=7.3782(8) A, b=5.5677(5) A, c=17.2466(17) A, beta=90.005(8){sup o}, Z=2. According to Liebau's nomenclature, the compound can be classified as a mixed anion silicate containing insular [SiO{sub 4}]-groups as well as [Si{sub 2}O{sub 7}]-dimers in the ratio 2:1, i.e. the crystallochemical formula can be written as K{sub 2}Ca{sub 6}[SiO{sub 4}]{sub 2}[Si{sub 2}O{sub 7}]. The silicate anions are linked by K- and Ca-ions distributed among five different non-tetrahedral M-positions and coordinated by six to eight nearest oxygen neighbors. Alternatively, the structure can be described as a heteropolyhedral framework built up by kroehnkite-type [M(SiO{sub 4}){sub 2}O{sub 2}]-chains in which the MO{sub 6} octahedra are corner-linked to bridging SiO{sub 4} tetrahedra. The chains (running parallel to [0 1 0]) are located in 4.6 A wide layers parallel to (1 0 0). Neighboring sheets are shifted relative to each other by an amount of +delta or -delta along [0 0 1]. In the derived two layer ...ABABAB... stacking sequence, chains belonging to adjacent sheets are linked by corner sharing of common oxygen atoms. The resulting network contains tunnels in which the more irregularly coordinated K- and Ca-ions are incorporated for charge compensation. A comparison between the present compound and structurally related mixed tetrahedral-octahedral frameworks is given. The characterization has been completed by Raman and FTIR-spectroscopy. An allocation of the bands to certain vibrational species has been aided by density functional theory (DFT) calculations. - Abstract: Side view of the whole heteropolyhedral framework in K2Ca6Si4O15. Display Omitted

• OSTI ID: 21372418
• Journal Information: Journal of Solid State Chemistry, Vol. 182, Issue 12; Other Information: DOI: 10.1016/j.jssc.2009.09.013; PII: S0022-4596(09)00448-4; Copyright (c) 2009 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ANIONS
CALCIUM IONS
CALCIUM OXIDES
CRYSTALLOGRAPHY
DENSITY FUNCTIONAL METHOD
INFRARED SPECTRA
LAYERS
MONOCLINIC LATTICES
MONOCRYSTALS
POTASSIUM OXIDES
RAMAN SPECTRA
SILICA
SILICATES
SILICON OXIDES
SPACE GROUPS
X-RAY DIFFRACTION
ALKALI METAL COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
CALCIUM COMPOUNDS
CALCULATION METHODS
CHALCOGENIDES
CHARGED PARTICLES
COHERENT SCATTERING
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CRYSTALS
DIFFRACTION
IONS
MINERALS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
POTASSIUM COMPOUNDS
SCATTERING
SILICON COMPOUNDS
SPECTRA
SYMMETRY GROUPS
VARIATIONAL METHODS