γAlB12, a new structure, and its relation toαAlB12as shown by twinned space groups
- 1 November 1961
- journal article
- research article
- Published by Walter de Gruyter GmbH in Zeitschrift für Kristallographie
- Vol. 116 (1-2) , 134-142
- https://doi.org/10.1524/zkri.1961.116.1-2.134
Abstract
A new AlB12 structure (γ) is described and its relation to α AlB12 defined. The γ structure is polytypically related to α AlB12 in having a 2-layer (rather than 3-layer) stacking along a normal to (101)α (≈ [201]α). The α–γ relationship involves cell twinning on every (101)α layer, using a normal to (101)α as the rotary twin operator, the latter being derived from space group considerations. Implications of the relationship are discussed, γ AlB12 crystals are hematitelike, lath-shaped, often syntaxically intergrown with α AlB12. The unit cell is orthorhombic with a = 16.56 Å, b = 17.53 Å, c = 10.16 Å, Z = 29, space group P212121. Morphological data are presented.Keywords
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