How can I make phase diagram with open O2


I’d like to make oxygen grand potential phase diagram of Li-Mn-P-O.
In this paper (S.P. Ong et al. / Electrochemistry Communications 12 (2010) 427–430) the open composition is O2. But in this web GUI, only O can available, is it means μO2?

Appreciate in advance for your help.

It means μ_O, according to the formalism documented here. I believe the equivalent μ_O2 (i. e. the μ_O2 that produces the same phase diagram) should be double μ_O. Note that these won’t correspond precisely to the publication because of differences in reference states.