Phase Diagram comic: part 5

Important note: if you are just joining us, you probably want to go back and start from the first page of the Phase Diagram comic!

With page 5, we’re nearing the end of the phase diagram adventure. This page explains open element phase diagrams in what I think is an intuitive (and perhaps new) way. Stay tuned for the next post, which will contain the full phase diagram comic (including the final page) and bring the journey to an end!


To be continued…

Further resources

“Thermal stabilities of delithiated olivine MPO4 (M = Fe, Mn) cathodes investigated using first principles calculations” by Ong et al.



If Li ion battery cathode materials (generally oxygen-containing compounds) release O2 gas from their lattice, it can lead to runaway electrolyte reactions that cause fire. Thus, a safe cathode material resists O2 release even under extreme conditions. Stated another way, safety is the “price point” (inverse O2 chemical potential) at which a cathode material will give up its oxygen. The higher the price point, the more stable the compound. This paper compares the critical chemical potential for O2 release between MnPO4 and FePO4 cathode materials, finding that similar chemistry and structure doesn’t necessarily imply similar safety.

“CO2 capture properties of M–C–O–H (M.Li, Na, K) systems: A combined density functional theory and lattice phonon dynamics study” by Duan et al.


The CO2 capture problem is to find a compound that absorbs CO2 from an open environment at chemical potentials found in industrial processes, and then releases the CO2 back into some other open environment under sequestration conditions. This paper constructs multi-dimensional phase diagrams to predict how different chemical systems will react with CO2 under different conditions.



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