Extended Data Fig. 4: Stoichiometry-dependent stability of (100) FAPbBr₃ surfaces.

a,b, Surface stability maps as a function of ligand and FABr concentrations computed for PC (a), and PEA (b) ligands. c–f, MD snapshots that illustrate three different regions observed on the stability maps. At high ligand+FABr concentrations, excess ions and ligands separate from the surface (blue area on the map) (c). As a result, the system acquires equilibrium stoichiometry corresponding to the green region on the map (d). At low ligand and/or FABr concentrations the surface becomes unstable again (a red region on the map) — segregation into two surfaces is observed for incomplete FABr passivation (f), whereas partial coverage solely with the ligand causes rupture of the PbBr underlayer (e). Ligand molecules in the snapshots are color-coded according to their binding mode — BM1 (blue), BM2 (green), BM2′ (orange), BM3 (red), unbound (black), and other (gray).