Pentacoordinated silicon in the high-pressure modification of datolite, CaBSiO4(OH)†,Inorganic Chemistry Frontiers

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Pentacoordinated silicon in the high-pressure modification of datolite, CaBSiO4(OH)†
Inorganic Chemistry Frontiers ( IF 6.1 ) Pub Date : 2018-05-04 00:00:00 , DOI: 10.1039/c8qi00257f
Liudmila A. Gorelova _{1,

2,

3,

4,

5} , Anna S. Pakhomova _{6,

7,

8,

9} , Georgios Aprilis _{9,

10,

11,

12,

13} , Leonid S. Dubrovinsky _{9,

12,

14,

15} , Sergey V. Krivovichev _{1,

2,

3,

4,

5}

Affiliation

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.

中文翻译：

高压钠钙石CaBSiO ₄（OH）改性中的五配位硅†

使用基于同步加速器的原位高压单晶X射线衍射，发现了硼硅酸盐硬硅钙石的一种新型改性剂CaBSiO ₄（OH）。从低压（I）到高压（II）的相变是等对称的，发生在27和33 GPa之间。锂铁矿-II的晶体结构包含五配位的Si原子，形成SiO ₅三角双锥体，它们共享边以形成Si ₂ O ₈二聚体。二聚体通过BO ₄四面体连接，产生[B（SiO ₄）OH] ^2-以前在无机化合物中未发现过的新型拓扑结构层。Datolite-II只是第二个无机结构，其中纯净地具有五重配位的Si。所得结果为硅酸盐的高压行为提供了新的线索，并表明冷压缩可被视为通往亚稳结构的低能途径，该结构可能具有异常和出乎意料的配位几何形状和拓扑结构。

更新日期：2018-05-04

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