Li{sub 2}Ca{sub 2}Si{sub 2}O{sub 7}: Structural, spectroscopic and computational studies on a sorosilicate

Journal Article · Fri May 15 00:00:00 EDT 2015 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/J.JSSC.2014.12.009· OSTI ID:22475589

Kahlenberg, Volker ^[1]; Brunello, Emanuele; Hejny, Clivia; Krüger, Hannes; Schmidmair, Daniela; Tribus, Martina ^[1]; Többens, Daniel M. ^[2]

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1. Institute of Mineralogy and Petrography, University of Innsbruck, Innrain 52, A-6020 Innsbruck (Austria)
2. Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Department of Crystallography, Hahn-Meitner-Platz 1, D-14109 Berlin (Germany)

Synthesis experiments in the system Li{sub 2}O–CaO–SiO{sub 2} resulted in the formation of single-crystals of Li{sub 2}Ca{sub 2}Si{sub 2}O{sub 7}. Structural investigations were based on single-crystal diffraction. At ambient conditions the compound has the following basic crystallographic data: hexagonal symmetry, space group P6{sub 1}22, a=5.0961(2) Å, c=41.264(2) Å, V=928.07(6) Å{sup 3}, Z=6. Structure solution was performed using direct methods. The final least-squares refinement calculations converged at a residual of R(|F|)=0.0260. From a structural point the lithium calcium silicate belongs to the group of pyrosilicates containing [Si{sub 2}O{sub 7}]-groups. Additional lithium and calcium cations are incorporated between the silicate dimers and are coordinated by four and six nearest oxygen neighbours, respectively. Each [LiO{sub 4}]-tetrahedron shares two common corners with directly neighboring tetrahedra forming zweier single-chains which are running parallel to 〈1 0 0〉 in z-levels defined by the presence of the 6{sub 1}{sup [0} {sup 0} {sup 1]}-screw axes. From the corner-sharing [LiO{sub 4}]- and [SiO{sub 4}]-moieties a three dimensional framework can be constructed. An interesting feature of this framework is the presence of an O{sup [3]}-type bridging oxygen linking three tetrahedra (one [LiO{sub 4}]- and two [SiO{sub 4}]-units). Structural similarities with other silicates are discussed in detail. The high-temperature behavior of the Si–O, Ca–O and Li–O bond distances in Li{sub 2}Ca{sub 2}Si{sub 2}O{sub 7} was investigated by in{sub -}situ single-crystal X-ray diffraction in the range between 65 and 700 °C. From the evolution of the lattice parameters, the thermal expansion tensor α{sub ij} has been determined. The structural characterization has been supplemented by micro-Raman spectroscopy. Interpretation of the spectroscopic data including the allocation of the bands to certain vibrational species has been aided by DFT-calculations. - Graphical abstract: Framework of [SiO{sub 4}]- and [LiO{sub 4}]-tetrahedra in the crystal structure of Li{sub 2}Ca{sub 2}Si{sub 2}O{sub 7}. - Highlights: • We report the crystal structure of the sorosilicate Li{sub 2}Ca{sub 2}Si{sub 2}O{sub 7} at ambient conditions. • The thermal expansion tensor as well as the evolution of the structure between 25 and 700 °C was studied. • A topological analysis of the tetrahedral framework based on [SiO{sub 4}]- and [LiO{sub 4}]-units is presented. • The crystal structure of Li{sub 2}Ca{sub 2}Si{sub 2}O{sub 7} is discussed with respect to related compounds. • Interpretation of the Raman spectra of the crystals has been aided by DFT-calculations.

• OSTI ID: 22475589
• Journal Information: Journal of Solid State Chemistry, Vol. 225; Other Information: Copyright (c) 2015 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
BOND LENGTHS
CALCIUM OXIDES
CALCIUM SILICATES
CATIONS
DIMERS
LATTICE PARAMETERS
LEAST SQUARE FIT
LITHIUM OXIDES
MONOCRYSTALS
RAMAN SPECTRA
RAMAN SPECTROSCOPY
SILICON OXIDES
SYNTHESIS
THERMAL EXPANSION
THREE-DIMENSIONAL LATTICES
X-RAY DIFFRACTION