Global stability is defined in terms of thermodynamic potentials, i.e. a material is globally stable if for a set of thermodynamic conditions, it is the global minimum of the relevant thermodynamic potential. For most practical cases, the relevant thermodynamic potential will be the Gibbs free energy, but others may be relevant depending on conditions. When considering global stability, it is important to note that the stability must be considered with respect to all competing phases-i.e. to both polymorphs of the same compositions, and to separation into multiple phases.