Annotations in ternary, 2D PDPlotter

pymatgen
,
1

Hi!
I am trying to add an annotation to a ternary, 2D phase diagram defined as:

with MPRester(key) as mpr:
    entries = mpr.get_entries_in_chemsys("Nb-Fe-Mn-O")
pd = GrandPotentialPhaseDiagram(entries, chempots=chempot)
fig = PDPlotter(pd).get_plot()
plot_data = PDPlotter(pd).pd_plot_data
lines, stab, unstab = plot_data

and say I’m interested in annotating some text next to an unstable entry. In order to do so, I’d gather the entry coordinates with

for entry, coords in unstab.items():
   # logic to select entry
    if chemsys == "Mn-Nb-Fe-O": # selecting only phases "inside" the ternary PD
        # do as follows

The issue arises when passing coordinates to traces: coords seems like a tuple of two cartesian coordinates. Passing coords as in

fig.add_annotation(
    x=coords[0],
    y=coords[1],
    text="my text",
)

doesn’t place the text in the right spot of the ternary diagram.
I suspect a conversion to ternary coordinates would be needed, utilizing the triangular_coord function as in

tern = triangular_coord(coords)
fig.add_annotation(
    x=tern[0],
    y=tern[1],
    text="my text",
)

but this also misplaces the text.

Seeking decomposition products to calculate manually the ternary coordinates also doesn’t work, as I get ValueError as ValueError: Mn2 Nb8 Fe2 O24 has elements not in the phase diagram Nb, Fe, Mn.

Is there a way to reliably annotate text on ternary, 2D phase diagrams?

Thank you!