Hi,
I’m looking into the anion corrections and have a few questions:
- Why are they only applied to anions? A. Wang et Al says
With the exception of Si, the corrections are all negative, indicating that uncorrected GGA and GGA+U energies generally underpredict the magnitude of the formation enthalpy, Hf . This underprediction is attributable to GGA’s overbinding of diatomic gas molecules
If the correction is because the gases are incorrectly predicted, shouldn’t we apply this to all instances of the atom. Is the reason for this that the energies of neutral atoms is also underpredicted?
2. Related question: why is the correction applied to species that aren’t diatomic gases in their natural states? For example Sb, Si.
3. Are most anion predictions just used for formation calculations? Table 1 says most anion corrections are just applied to “anion cpds” (meaning chemical potential diagrams). Does this mean they don’t affect the formation energies? I think MP Compatibility and energy corrections (below) suggests that the answer to this is yes, but worth putting here for someone with a similar question I guess.
- For oxides / peroxides / superoxides, we shift the compound energy rather than the gas energy. This is done so that we can have different shifts depending on the type of oxygen bond that arises in the compound, and it is called an
AnionCorrection
- Is there a way to view the corrections applied to a specific material/formation energy?
Thanks!