The distribution of gallium/germanium in the type-I clathrates Sr_(8)Ga_(16)Ge_(30) and Sr_(4)Eu_(4)Ga_(16)Ge_(30) over the three crystallographically distinct framework sites has been determined by resonant diffraction. The analyses indicate a strong preference for the occupation of the 6c site by gallium. This is consistent with theoretical predictions, but contrary to the results of a previous neutron diffraction study. The gallium distribution, and, hence, the thermoelectric properties of these materials, may be amenable to manipulation by heat treatment.
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