In this study, we are concerned with the n-type dopability of Ba 2(1 x) Sr 2x CdP 2 alloys. We chose to verify the n-type dopability of Ba 0.75 Sr 1.25 CdP 2 (x = 0.625), which lies in the optimal composition range of x = 0.35 0.70 based on the electronic and thermal transport properties (Sections 2.2, 2.3). The periodic supercell approach utilized in first-principles calculations of defect energetics is well established for ordered and stoichiometric materials. A direct extension of the supercell approach to alloys is not straightforward because of the presence of different local environments in the disordered structures. As such, DFT relaxations of hundreds of supercells may be required to compute the defect formation energetics in alloys, which makes this approach prohibitively expensive. For example, in a 100-atom SQS supercell of Ba 0.75 Sr 1.25 CdP 2 , there are 25 unique Sr sites. Therefore, calculating the formation energy of Sr vacancies (V Sr ) in a single charge state (typically, multiple charge states of each defect are calculated) amounts to 25 different DFT supercell relaxations. It quickly becomes apparent that considering all types of defects, including vacancies, anti-sites, and interstitials, in different charge states requires hundreds of DFT supercell calculations. Furthermore, in a disordered material, the different local environments can lead to variations in the formation energies of the same defect. Therefore, it is fundamentally important to determine the statistical variation in the defect formation energies.