Of course, happy to help. For the second question, if e_above_hull is 0, it means the structure is stable with respect to decomposition at the same, fixed composition. See “Energy above hull” in our glossary, which explains in a bit more detail. If you’ve got an open system to one element, for example, the stability profile might be a bit different, and depends on the chemical potential of the open element.
The first question is a bit more complicated. The energies above hull for each material are generated using the phase diagram code in pymatgen. To do this, you basically need some expression of the potential energy of the material that’s consistent with the MP dataset. We don’t have a scheme for predicting the potential energy of an arbitrary structure, but you could do it three different ways in my mind.
1). Submit your structure to MPComplete via the Crystal Toolkit. There’s a bit of a backlog in MPComplete right now due to our DB infrastructure transfer that’s ongoing, and there’s at least some probability that the calculation will fail, but if it’s successful, the result will eventually be added to the website with the appropriate stability data.
2). If you’re able to do a VASP calculation, you can use either atomate or VASP directly with pymatgen’s input sets to perform a DFT calculation that should be equivalent to what we’ve done. Using the output of the VASP data, you can process the resultant ComputedEntry using the MaterialsProjectCompatibility class of pymatgen’s compatibility module, and then generate your own phase diagram.
3). If you know the heat of formation of your compound or the heat of reaction from some other set of known compounds already in MP, you should also be able to generate a ComputedEntry by calculating a total energy from some set of references, rather than doing a VASP calculation.