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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.

Volume 4| Part 5| September 2017| Pages 671-677
ISSN: 2052-2525