µ bulk CFO depends on the experimental conditions, but it can be approximated as the total energy E bulk CFO per formula unit of the bulk phase at T = 0 K and p = 0 atm. Here, it is directly derived from our DFT calculations. Thus, there are only two independent chemical potentials remaining. Additionally, the chemical potentials µ i of the three species in the ternary oxide are referenced to the energy in their respective bulk/gaseous reference phases: