Reaction energy calculations

[Yi_Tzu_Wu]

Dear Materials Project

I used two ways to calculate reaction energy of the reaction Li6PS5Cl → Li3PS4 + S + LiCl + 2 Li: (1) app “Reaction Calculator” and (2) final energies of these compounds in app “Materials Explorer”. However, the two ways have different reaction energies. Please see the following calculation details.

(1) App “Reaction Calculator” shows the reaction energy of 3.394 eV.

(2) Using app “Materials Explorer”, I used the final energies of the most stable phase of each element/compound to calculate the reaction: Li6PS5Cl (mp-985592) → Li3PS4 (mp-985583) + S (mp-96) + LiCl (mp-1185319) + 2 Li (mp-1018134), and the reaction energy of 2.8906 eV is different from that of 3.394 eV of “Reaction Calculator”.

(-4.3976 x 8) + (-4.1364) + (-3.7087 x 2) + 2 x (-1.9089) - (-4.111 x 13) = 2.8906 eV

I would like to ask if there is anything I missed or misunderstood.

Thank you so much!

[mattmcdermott]

Hi @Yi_Tzu_Wu,

Your reaction energy calculation is indeed set up correctly, but you seem to be using the Final Energy/Atom for each entry, which does not have corrections applied. Instead, you should use the Corrected Energy. Note that this is not on a per-atom basis, so you will not need to multiply by the number of atoms. Once you use these corrected energy values you should get the same answer.

FYI: This will be much clearer on the new MP site which is being released soon. For example, for mp-985592 under Thermodynamic Stability > How was this formation energy calculated? it shows this: