The distinct free energy landscapes of the lithium halides underscore the structural analogies and disparities between the various halides. In general, computational models predict multiple structures to be accessible to Li 4 X 4 regardless of the nature of the halide. As expected, increasing the solvation of Li 4 X 4 weakens or cleaves Li-X bonds. The solvent enters the first coordination sphere of lithium, mostly forming standard THF-Li terminal bonds; but THF may also assume bridging positions between two accessible lithium atoms, leading to a very high diversity of structures. In all cases, solvent substitution tends to follow a dissociative mechanism, with an initial elongation of the Li-X bond followed by the coordination of a THF, even though long-living under-coordinated Li intermediates are not observed during MD simulations. The preference for compact species like the pseudocubane declines from Cl to Br to I. The fact that the crystallization of the pseudo-cubanes Li 4 X 4 (S) 4 (S = solvent) have been characterized for the three halides by X-ray diffraction for S = Et 2 O solutions illustrates the insightful comment by D. Seyferth that aggregates found in the crystalline state may not survive in Table Halogen atomic charges, computed with the CM5 method, for different Li coordination spheres in LiX salts (Li in yellow, X in black, and THF as transparent sticks). solution. Additionally, the observation of pseudo-cubanes in the solid state for all three halides suggests that their absence in solution, particularly for iodide, is not due to an intrinsic destabilization for the heaviest halide. Instead, there is a solvent-or dynamic-driven preference for more solvated and, thus, smaller aggregates. Another marginal difference between the calculated and observed structures is that the ladder-type structure was not identified as a possible structure in solution while it has been reported for [LiCl(pyridine)]n, Li 4 Br 4 (2,6-dimethylpyridine) 6 42 and [LiI(THF)]n. Calculations identify only the boat form B6 for X = Cl and Br, a structure also observed in the crystalline state for [LiCl(THF)]n and [LiBr(THF)]n. Numerous factors determine the diversity in the aggregate sizes. Since many structures are common for the three halide systems, a reasonable hypothesis is to consider that the variation of the entropy term does not depend significantly on X. Therefore, one can focus on the enthalpic contribution. One noticeable difference between the three Li-X species is that the Li δ + -X δ - charge polarization decreases from Cl to Br to I as shown for any given structure in Table and Figure . Furthermore, this charge polarization is larger in smaller aggregates and in more open species where fewer halides are bonded to a given lithium. In particular, there is a significantly larger charge polarization in the LiX monomer relative to the Li 2 X 2 dimer. Cleaving an Li-X bond is systematically associated with coordinating an additional THF to Li. The replacement of a Li• • • X interaction by a Li-THF coordination is likely to be energetically more favorable when the Li-X ionic character is minimized because the Li-X and Li-(THF) bond characters would be more similar. This favors the cleavage of Li-X and the increased solvation for heavier halides, as reported by the different solvation of the three halides salts (Figure ). It should be kept in mind that the solvent also has a stabilizing influence on the halide, which increases from Cl to Br to I. The dispersion interaction energy between THF and X is evaluated in the case of monomeric Li-X, yielding -7(3), -14(3), -18(4) kcal mol -1 for X = Cl, Br, I, respectively (Figure and Table ). Dispersion interaction has no preferential directionality and its increase is mostly due to the higher polarizability of the heavier halides. The outcome of these effects is that a LiX aggregate with greater ionic character within the Li-X bond tends to prefer polynuclear forms with numerous Li• • • X interactions. In contrast, with heavier X and an associated less ionic character of the Li-X bond, the Li• • • X interaction is more in competition with Li• • • THF coordination supplemented by X• • • THF interplays, and the fragmentation of the polynuclear aggregates into smaller units becomes more favorable. However, this fragmentation reaches a limit since the Li-X ionic character is higher in smaller units. This is why the monomer is not found on the free energy maps as an accessible species, on its own, within the energy range considered in the study, the exception being for X = I where it occurs at higher energy (∆A≈ 5 kcal mol -1 ) and thus in a relatively smaller concentration. For the other halides, the dimeric species is the smallest aggregate identified as energetically accessible. Finally, it is interesting to remember that the solubility of LiX in organic solvents increases from Cl to Br to I. While this study does not address the topic of solubility of these ionic salts, the parallel between our results and the trend in solubility is enthralling. Certainly, the favored fragmentation of large aggregates participates in the solubilization of LiX.