Figure shows the variation of occupation of all classes of site (D4R, adjacent and framework sites), in addition to the asymmetry, which is depicted as a comparison between maximum and minimum D4R occupation. By comparing two specific germanium loadings: sufficient to fill half, and sufficient to fill all D4R units, we find that there are two apparent modes of germanium distribution: i) strong preference for D4R occupation (half-filling of D4Rs), and ii) the spread of the occupation towards the framework T-sites (complete filling of D4R). These modes are clearly discernible from the relative occupations of the different classes of T-sites (Figure ), which, with the exception of UTL, show that the relative occupations of D4Rs peak approximately at Si/Ge ratios corresponding to the half-filling of D4R units and then plummet and stabilize again approximately at the Si/Ge ratios corresponding to complete-filling of D4R units. This behaviour of D4R occupations is approximately mirrored by the occupations of framework T-sites, with the occupation of the adjacent T-sites being close to constant across all the Si/Ge ratios. For Si/Ge ratios corresponding to more than the complete-filling of the D4R units (again with the exception of UTL), the occupations of various classes of T-sites are rather stable and tend to their respective (purely statistical) class multiplicities (highlighted in Figure on the right ordinate axis).