I was trying to understand some indicators about the stability of materials (that basically tell you whether it can be synthesized or not.. right?).

Specifically, I'm trying to link the knowledge of formation energy and energy above convex hull.

Can you explain me a little better and eventually make some examples of value ranges for these two parameters (formation energy and energy above convex hull)?

I'm asking because I'm trying to put up some datasets to work with but still have little domain knowledge.



1 Answer 1


Basically, convex hull is a plot of formation energy with respect to the composition which connects phases that are lower in energy than any other phases or a linear combination of phases at that composition. Phases that lie on the convex hull are thermodynamically stable and the ones above it are either metastable or unstable. This plot can only give an idea about the stability of the structure at 0 K. Higher temperature calculation (Phonopy is one of the codes) can assure the stability of the given structure at the working temperature (mostly greater than 0 K).

Hope it helps.

  • $\begingroup$ thank you very much, could you clarify what you intend by phases in this context? $\endgroup$ Jun 7, 2021 at 13:08
  • $\begingroup$ I intended to consider the formation energy of the compounds. For example : suppose A and B are two elements, then AB, A2B, A3B etc. are some of the compounds. $\endgroup$ Jun 9, 2021 at 17:21
  • $\begingroup$ Can I ask also what do you intend when you say Phases 'above' the convex hull? $\endgroup$ Aug 16, 2021 at 11:27
  • 1
    $\begingroup$ So convex hull is the line connecting the more negative energy phases at that specific composition. Suppose we have some compounds of A and B i.e., AB, A2B etc. Let say AB has different structure i.e., FCC and HCP. Then if the energy of HCP-AB is more negative than FCC-AB then HCP-AB will be on the convex hull at the composition of 0.5 A. FCC-AB will have a less negative energy at the same composition and it won't be a part of the convex hull. $\endgroup$ Dec 7, 2021 at 12:19

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