The cations (Ba, Sr) can occupy two distinct Wyckoff positions in the Ba 2(1 x) Sr 2x CdP 2 structure (sites 1 and 2 in Figure ). To model the site selectivity of the cation disorder, for each composition, we considered different SQS supercells with the disorder constrained to a specific Wyckoff site. Given the equal stoichiometric ratio of sites 1 and 2, for the 50-50 alloy, only one SQS supercell with disorder on both sites was considered. Each SQS supercell was fully relaxed (volume, cell shape, and atomic positions) with DFT using the functionals and parameters described in Section 4.1.