A mixture stability criterion asserts that a mixture of at least two redox elements in a crystal lattice will be unstable during charge and discharge cycles unless a set of charged ground state configurations at a specified value of a mixing ratio for the redox elements and a set of discharged ground state configurations at the same value of mixing ratio both consist of the same derivative superstructures. All members of the charged ground state set and all members of the discharged ground state set are within a same energy threshold value of the lowest-energy member of each set. The value for the energy threshold may represent a value of thermal energy calculated with Boltzmann's constant. Examples of alternative embodiments include a method for implementing the mixture stability criterion, computer hardware adapted to perform a method embodiment, and computer-readable media including a method embodiment.