In this study, we selected 19MgCl2/4TiCl4/5ID systems as the main target of structure determination based on the following considerations. Firstly, experimental observations indicate that the lateral dimension of the primary particles is at least 2-3 nm, corresponding to approximately 50 MgCl2 units. However, the addition of donor molecules significantly increased the computational cost, making structure determination for such a large system infeasible with our available computational resources. Nonetheless, it was reported that important conclusions, such as structural reconstruction and diversification due to chemisorption, are insensitive to the system size, except for extremely small systems below 10 MgCl2. Secondly, based on the primary particle size and chemical composition of actual catalysts, the total number of TiCl4 and donor molecules is roughly estimated to be 50-80% of the coordinatively unsaturated MgCl2 sites. Lastly, the typical molar ratio of ID to TiCl4 in catalysts is 1 mol/mol or slightly larger. Considering all these factors, 19MgCl2/4TiCl4/5ID offers a similar coverage to the real catalyst, while keeping the structure size at a reasonable level for computational reasons. We adopted two bifunctional IDs, diethyl phthalate (DEP) and 9,9-bis(methoxymethyl)fluorene (DE) not only for their industrial relevance but also for their distinct characteristics. In comparison to phthalate, 1,3-diether has a shorter interfunctional distance, leading to limited availability for bridging adsorption and a narrower molecular weight distribution of PP. Andoni et al. reported these two donors exhibited significant differences in the morphology of MgCl2 crystallized from an ethanol solution. It is expected, then, that the support reconstruction will be significantly different between the two IDs, offering comparison points to better understand how the ID shapes the MgCl2 support. As reference systems, we considered: 19MgCl2 and 19MgCl2/4TiCl4, whose structures were previously determined by us, and 19MgCl2/9TiCl4 (having the same coverage as the IDcontaining systems), whose structure was determined in Figure .