Similarly to the case of D4R occupation by germanium, we introduced the excess Ge-Ge coordination number (see Section 2.3 for definition), which partially decouples the increase in germanium clustering from the increase in germanium content, by measuring the difference between the observed Ge-Ge CN values and those based on the assumption of purely random (uniform) germanium distribution across all T-sites (see Figure ). Figure confirms that germanium prefers to cluster for all Si/Ge ratios considered, with a germanium atom being surrounded by between 0.4 and 1.2 more germanium atoms as nearest neighbours than would be predicted based on a random germanium distribution, at intermediate to high germanium loading (Si/Ge ≤ 8). Compared to the D4R occupation preference (see Figure ), the germanium clustering peaks at lower Si/Ge ratios (≈ 3-4) and either stays flat after that (CTH) or decreases only mildly (IWW, UTL, BEC, UOV). The clustering preference can be related to the increased energetic stabilization associated with phase separation of germanium as exemplified by a strong positive correlation (with Pearson correlation coefficient 36 R ≈ 0.5-0.8) between stabilization of the structure and a total count of Ge-O-Ge bonds (see SI Figures S8 S50), an alternative measure of clustering used in the literature . In brief, our simulations suggest a significant clustering tendency of germanium, irrespective of the specific structural unit, across all the Si/Ge ratios considered.