Here, the total energy of a unit formula is indicated by E tot . Moreover, x i is the number of atoms and E i is the energy of the i th element. The sum of x i provides the number of atoms in a unit formula, which is 8 for BaCuF 6 and 13 for A 6 MO 6 . To calculate E i for each species, we used the Pymatgen code to collect the most stable structure of each element. E form indicates the thermodynamic stability of a material against its elements. The negative E form in Table reflects that all four materials are stable. It is also clear that E form increases as