 # Grand Potential Phase diagrams and interfacial reactivities

Dear All,

I have some questions about the grand potential phase diagrams and the interfacial reactivities. So, as in one of my previous posts, I log in with the materials project API key and I generate entries for my phase space of interest. In the normal PhaseDiagram, both of my compounds ‘A’ and ‘B’ appear as stable compounds.

Now I want to check If both of those compounds would decompose into other products when as a function of lithium chemical potential. So I just do the following

``````mp_entries = rester.get_entries_in_chemsys(["my phase space"])

c1 = Composition('A')
c2 = Composition('B')

li_entries = [e for e in mp_entries if e.composition.reduced_formula == "Li"]
uli0 = min(li_entries, key=lambda e: e.energy_per_atom).energy_per_atom

eli = Element('Li')
``````

Then I scan over different voltages going.

``````voltages = np.linspace(0.0,10.0,50)

for voltage in voltages:
gpd = GrandPotentialPhaseDiagram(mp_entries,{eli:(uli0 - voltage)})
irg = InterfacialReactivity(c1,c2,gpd)

print(str(uli0 - voltage) + ' ' + str(ir.labels()))
``````

But what I get, no matter which is the voltage modifying the lithium chemical potential is the following

``````{1: 'x= 0.0 energy in eV/atom = 0.0 A -> A', 2: 'x= 1.0 energy in eV/atom = -0.0 B -> B'}
``````

Which does not make a lot of sense (as long as I am understanding this function correctly), since decomposition is definitely inevitable at such large voltages.

My questions is more related to if I am even using this functionalities correctly. And if so, where do you think the error is.

Best regards,

Oier