Crystal structure of α-AlB 12
Abstract
The crystal structure of α-AlB 12 (tetragonal; a = 10.158(2) Å, c = 14.270(5) Å, space group P4 12 12 or P4 32 12) has been determined by the single-crystal X-ray diffraction method. It was solved by the Fourier technique initially based on a partial B 12 icosahedral structure, which was inferred from crystal chemical considerations. Refinement was made with the aid of a full-matrix least-squares program leading to a final R value of 3.0%. The structure is based on a three-dimensional framework consisting of B 12 icosahedra, B 19 units, and single B atoms; the B 19 unit is a twinned icosahedron with a triangular composition plane and a vacant apex on each side. The chemical unit is Al 3.2·2B 12·B·B 19 and its number in the unit cell is 4. The Al atoms are distributed statistically over five sites in the boron framework. The occupancies of the sites are 72, 49, 24, 15, and 2%, respectively.
- Publication:
-
Journal of Solid State Chemistry France
- Pub Date:
- January 1977
- DOI:
- 10.1016/0022-4596(77)90052-4
- Bibcode:
- 1977JSSCh..20...67H