Pourbaix digram entry with a wrong composition

pymatgen
1

Hi,

I recently encountered a problem that the pourbaix diagram sometimes includes the multientry with a different composition than the one initially used to generate the pourbaix diagram. This only occurs for some initial compositions. What could be the reason for this?

Also, in the example shown in the attached screenshot, the multientry includes both Fe(s) and Fe[+2] at the same time. It looks unphysical, but could this be a bug in the code?

Screen Shot 2023-03-03 at 1.02.24 PM
Screen Shot 2023-03-03 at 1.02.24 PM1014Ɨ622 98 KB

Thank you

1 Like
2

Hi Johan - appreciate the detailed example - could you paste the code as text, just so I can be sure Iā€™m copying it exactly?

3

Here it is.

ELEMENTS_HO = {Element("H"), Element("O")}
chem_sys = 'Fe-Ir-Li-Si-V'
pourbaix_entries = mpr.get_pourbaix_entries(chemsys=chem_sys)
pourbaix_elem = [Element(elem) for elem in chem_sys.split('-')]

conc_dict = {}
for elem in pourbaix_elem:
    conc_dict[elem.symbol] = 1e-6

comp_dict = Composition({Element('Fe'): 1, Element('Ir'): 1, 
             Element('Li'): 2, Element('Si'): 1, Element('V'): 2, }).fractional_composition
print(comp_dict)

pbx = PourbaixDiagram(pourbaix_entries, comp_dict=comp_dict, conc_dict = conc_dict)
pbx_comp = Composition(pbx._elt_comp).fractional_composition
print(pbx_comp)
for multientry in pbx.all_entries:
    entry_pbx_comp = Composition(
        {elt: coeff for elt, coeff in multientry.composition.items() if elt not in ELEMENTS_HO}
    ).fractional_composition
    if entry_pbx_comp != pbx_comp:
        print(multientry)
        print(entry_pbx_comp)
        exit()

Thank you!