• os-κMP2 correlation energy density, ẽκMP2 c,os (r) = e κMP2 c,os (r) ρ -1/3 (r)e x (r) . As noted in the main paper, we use eight small closedshell atoms/ions (H -, He, Be, Mg, Ne, Ar, Ca, and Kr) to train ML2. For ML2's validation, we select ions of similar size to the training set (Li+, Ca2+, and Ne2+). prediction of correlation energies gets worse at larger interatomic distances with increasing training epochs. Furthermore, the energy error is one order of magnitude higher in comparison to the results from the LES-based predictions in Fig. , underscoring again the advantage of LES over GES.