Question About the Function "get_decomp_and_phase_separation_energy"

pymatgen
1

Hello,

I have a question about the function “get_decomp_and_phase_separation_energy.”
Is it acceptable if the atomic ratio differs before and after decomposition?

For example, in the decomposition of LiScVO₄, when compared to 5/42[V₂O₃] + 8/21[Li₃VO₄] + 1/7[VO₂] + 5/14[Sc₂O₃], the atomic ratio does not seem to match.

Another example is when Ni₃S₄ (mp-1050) and S (mp-96) are mixed in a 0.66:0.33 ratio, the function returns a reaction where NiS₂ (mp-1180046) and S (mp-96) are produced in a 0.6:0.4 ratio.

Before the reaction, the Ni:S ratio is 4:16, but after the reaction, it becomes approximately 1:12.6.

Could you explain why these discrepancies occur?

Best,

2

Hello,

See this page explaining how the atomic fractions are calculated (Fractions of decomposition products). Essentially each entry has to be normalized to 1 atom.

For example, with LiScVO4, it has 7 atoms. Hence, normalizing it per atom results into Li(1/7)Sc(1/7)V(1/7)O(4/7).

If we look at just Li in 8/21(Li3VO4):

8/21*(Li(3/8)) = 3/21 Li = 1/7 Li

Which is the fraction we have for LiScVO4.

As for the example of Ni3S4, could you explain more what you mean by mixing it at a 0.66:0.33 ratio? What does the reaction equation look like?

I hope this helps somewhat!

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