The association of two tetrameric structures into an aggregate of 8 Li and 8 Cl nuclei requires an energy of 3.1(2) kcal mol -1 and leads to a stabilization of 16.1(8) kcal mol -1 , while the addition of a third tetrameric structure has an energy barrier of 3.4(3) kcal mol -1 and leads to a further stabilization of -10(1) kcal mol -1 . These two larger aggregates display units in hexagonal packing, as previously observed in polymeric solvent-separated crystals of LiCl in tetramethylethylenediamine. Low molecular weight aggregates in hexagonal packing have also been shown to form in the early stages of NaCl crystallization, preceding rock salt (FCC) formation (Figure ). These features suggest an initial nucleation stage of LiCl at a concentration close to, but still lower than, the saturation point. At the same time, quantum chemical calculations yield energies consistent with those predicted by the MLP (Table ). While this confirms that the MLP is able to reproduce data of quantum chemical quality, it also means that any shortcoming in the quantum data used for training is inherited by the MLP. For larger aggregates containing several halide nuclei, strong dispersion forces are hard to reproduce accurately with density functional theory, even with dispersion corrections. 107