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First-principles density functional calculations are used to study the nucleation and stability of L1₂-ordered precipitates in Al–Sc–Li alloys. For dilute Al alloys, there are three possible ordered L1₂ precipitates: Al₃Sc, Al₃Li and an Al₃Sc/Al₃Li core/shell structure. To calculate the nucleation behavior, information about bulk thermodynamics (both static total energies and vibrational free energies), interfacial energetics and coherency strain is required. The study finds the following: (1) the coherency strain energies for forming coherent interfaces between Al/Al₃Sc, Al/Al₃Li and Al₃Sc/Al₃Li are relatively small, owing to the small atomic size mismatches in these systems; (2) the sublattice site preferences of Sc and Li are calculated, and it is demonstrated that Sc and Li share the same sublattice sites in both Al₃Sc(L1₂) and Al₃Li(L1₂), in agreement with recent experimental results; (3) the calculated solubilities of Sc and Li …