The germanium distribution in the CTH(-A) structure (polymorph A from the * CTH intergrowth family), composed of dense CFI layers connected by D4R units, is characterized by a tendency of germanium to phase-separate along the [0b0] direction (see Figure ), forming a germanium-rich D4R unit (and/or CFI layer) and a germanium-poor D4R unit (and/or CFI layer) -there are two D4R units and two CFI layers included in the periodic simulation cell discussed herein. At low germanium content (up until Si/Ge ≈ 7), similarly to other frameworks, the D4R occupation is strongly preferred (Figure ), represented predominantly by the clustering of germanium in one of the two D4R units in the unit cell (see, e.g., the global structure optima in Figure ), although various other germanium distribution patterns (partial occupation of both D4R units or even predominant occupation of the CFI layers -see also SI Figure ) are also observed to be rather stable (within 10 kJ/mol of the GSO). The observation of this near-degeneracy (in energy) between rather distinct germanium distributions contributes to the fact that the average Ge count in D4R does not exceed four Ge atoms even in the germanium-rich D4R up until Si/Ge ≤ 2.5 and that the CFI layers become more abundant in ger-manium than D4R units already for Si/Ge ≤ 5. Indeed, for high germanium loading, the structures with the germanium predominantly filling the CFI layers (e.g., the site Si6 being particularly attractive to Ge) become almost isoenergetic with the structures in which one D4R is rich in germanium accompanied by a small number of spillover germanium atoms nearby (SI Figure ).