I understand that energy above Hull is a measure of material’s (or structure’s) stability. I believe if this figure for a particular material is greater than 0 in the calculations, you have listed it as more or less unstable, or a decomposing material.
So does this decomposing refer to the room temperature, or at some temperature in general?
For an example, the Pm-3m structure of BaTiO3 cannot be stable at room temperature? Because the E_above_Hull > 0 ?