 | Acta Crystallographica Section B Acta Crystallographica Section B STRUCTURAL SCIENCE, CRYSTAL ENGINEERING AND MATERIALS |
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![[Figure 1]](wf5116fig1mag.jpg)
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Figure 1
Polyhedral representations of disordered sillimanite (left, hypothetical) and a local motif of the mullite structure (right), viewed along the c-axis, rotated 6° about a- and b-axes. (a) In the hypothetical disordered sillimanite the pairs of TO4 tetrahedra (diclusters, light blue) are occupied by equal fractions of Si and Al. O3 links the tetrahedra in each dicluster. In mullite Si4+ is partially replaced by Al3+, requiring the formation of O3 vacancies. The arrows highlight two TO4 which are shifted to a new position in mullite, forming two T*O4 tetrahedra (red) in (b) where each new group of two slightly distorted TO4 (magenta) and one T*O4 forms a tricluster. The O3 vacancy in between is represented by a large white semitransparent sphere. |
![[Figure 1]](wf5116fig1.jpg)
| STRUCTURAL SCIENCE CRYSTAL ENGINEERING MATERIALS |
ISSN: 2052-5206
