Thank you very much for your response and helpful comment.
At first, I set the VASP input parameters manually. Later, after reading several forum posts related to Ehull calculations, I switched to using the MPRelaxSet module from pymatgen to generate the input files.
The structure I’m working on is Na₂ZrCl₆, which is not available on the Materials Project. According to literature, it adopts a P2₁/c space group. Since no direct structural file was available, I built the POSCAR by modifying structures from Na₃ErCl₆ and Na₂ZrF₆ as templates.
Based on the OUTCAR, I confirmed that the calculation uses the GGA-PBE functional. I did not apply any Hubbard U corrections, as the system does not contain strongly correlated electrons.
In addition, I found a publication reporting the Ehull of Na₂ZrCl₆ is about 25 meV/atom, which supports its metastable nature.
Please let me know if you have further suggestions or if there’s anything I might have overlooked. I appreciate your feedback.
Best regards,
fei