Fig. 4: Classical molecular dynamics and density functional theory calculations.

a–d Selected configurations of ions in isopropyl solution a MA⁺, b FA⁺, c I^- and d Br^-. The yellow shadow is added to help identify the ions in the solution. Initial, intermediate, and final structures along with the CRs bringing to e–i MAPbI₃, k and l–p MAPbBr₃ and k and n–q FAPbBr₃. The first block of panels e–i and k–q shows the lateral view of the precursor PbI₂ and PbBr₂ structures, putting in evidence the (quasi)-layered structure where intercalation of A⁺ and X^- takes place. The second block shows A⁺ and X^- ions intercalated in the precursor. The third block highlights the MAI-PbI₂ and MABr-PbBr₂ intermediate phases. Finally, the fourth block shows the final products, the perovskite structures. j Energy diagram of the stable and metastable phases formed along the conversion reaction PbX₂+A⁺_sol+X^-_sol → APbX₃ (see also Supplementary Table 2). The energy of reactants, AX_sol + PbX₂, in particular the energy of solvated A⁺ and X^- ions, is obtained from DFT calculations of configurations extracted from extensive Classical MD simulations (see the Methods).