A closer look into close packing: pentacoordinated silicon in a high-pressure polymorph of danburite

Pakhomova, A.; Bykova, E.; Bykov, M.; Glazyrin, K.; Gasharova, B.; Liermann, H.-P.; Mezouar, M.; Gorelova, L.; Krivovichev, S.; Dubrovinsky, L.

doi:10.1107/S2052252517010612

Figure 3
The evolution of silicon-based structural units along the high-pressure treatment of danburite. (a) Distortion of an Si₂O₇ ditetrahedral group from 1.1 (1) to 22.6 (1) GPa. Note the respective increase in the O3—O4—O3 angle from 148.81 (2) to 174.57 (2)° that causes the anomalous enlargement of the c axis along the compression. (b) A chain built of SiO₅ trigonal bipyramids in the structure of danburite-II (Pnam) at 25.4 (1) GPa. (c) A chain built of edge-sharing SiO₆ octahedra in danburite-III ( $[P{\overline 1}]$ ) at 25.4 (1) GPa. The Si—O bond distances are given in ångströms.

IUCrJ

Volume 4| Part 5| September 2017| Pages 671-677

ISSN: 2052-2525

https://doi.org/10.1107/S2052252517010612

CHEMISTRY | CRYSTENG

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