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Issue 7, 2018
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Pentacoordinated silicon in the high-pressure modification of datolite, CaBSiO4(OH)

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Abstract

A new modification of borosilicate datolite, CaBSiO4(OH), has been discovered using synchrotron-based in situ high-pressure single-crystal X-ray diffraction. The phase transition from low (I) to high (II) pressure modification is isosymmetric and occurs between 27 and 33 GPa. The crystal structure of datolite-II contains pentacoordinated Si atoms forming SiO5 triangular bipyramids that share edges to form Si2O8 dimers. The dimers are linked through BO4 tetrahedra, resulting in the [B(SiO4)OH]2− layers of a novel topology that has not previously been observed in inorganic compounds. Datolite-II is only the second inorganic structure that contains Si in purely fivefold coordination. The results obtained shed new light on the high-pressure behaviour of silicates and demonstrate that cold compression can be considered as a low-energy pathway to metastable structures, which might possess unusual and unexpected coordination geometries and topologies.

Graphical abstract: Pentacoordinated silicon in the high-pressure modification of datolite, CaBSiO4(OH)

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Publication details

The article was received on 22 Mar 2018, accepted on 03 May 2018 and first published on 04 May 2018


Article type: Research Article
DOI: 10.1039/C8QI00257F
Citation: Inorg. Chem. Front., 2018,5, 1653-1660
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    Pentacoordinated silicon in the high-pressure modification of datolite, CaBSiO4(OH)

    L. A. Gorelova, A. S. Pakhomova, G. Aprilis, L. S. Dubrovinsky and S. V. Krivovichev, Inorg. Chem. Front., 2018, 5, 1653
    DOI: 10.1039/C8QI00257F

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