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Abstract:
The clathrate-I phase Ba8AlxSi46-x has been structurally characterized
at the composition x = 6.9 (space group Pm (3) over barn, no. 223, a =
10.4645(2) angstrom). A crystal structure model comprising the
distribution of aluminium and silicon atoms in the clathrate framework
was established: 5.7 Al atoms and 0.3 Si atoms occupy the
crystallographic site 6c, while 1.2 Al atoms and 22.8 Si atoms occupy
site 24k. The atomic distribution was established based on a combination
of Al-27 and Si-29 NMR experiments, X-ray single-crystal diffraction and
wavelength-dispersive X-ray spectroscopy.
