PourbaixDiagram Concentrations

Are the concentration inputs to PourbaixDiagram in mol/kg or M? Does it vary between the app and the documentation?

’ The default concentration of ions is 10![^{-8}] M’ in documentation

‘Concentration in mol/kg’ in app

Hi @Kirby_B, thanks for bringing this discrepancy to our attention. In our PourbaixDiagram app (and associated code in pymatgen), the concentration technically is set equal to the activity, because we assume unit activity coefficients. So rigorously speaking, neither M nor mol/kg units are correct.

As a practical matter, as long as you are at relatively low concentrations there will be very little difference between the two, and the assumption of unit activity coefficients is relatively accurate. I typically think in terms of Molarity when using the app.

This is an area of the PourbaixDiagram code that we’re working on improving, and we welcome any suggestions or contributions. Hope that helps!