Issue with Fe L2 and L3 Peaks on XAS Plot in Fe1.0Mo3S13 and Fe0.5Mo3S13

[emmanuel_adejumo]

Dear VASP Team,

I hope this message finds you well. I am currently working on an XAS calculation for Fe and have encountered an issue when trying to observe both the L2 and L3 peaks on the same plot. Despite applying an energy shift, I am unable to align the two peaks correctly.

The peaks appear, but they do not correspond to the expected energies for L2 (719.9 eV) and L3 (706.8 eV). Could you please provide some insights or suggestions on why this misalignment might be occurring, and how I can correct this issue to properly visualize the L2 and L3 features?

Thank you for your time and assistance.

[ahampel]

Hi,

thank you for reaching out to us on the official VASP forum.

Could you clarify what you mean by: "but they do not correspond to the expected energies for L2 (719.9 eV) and L3 (706.8 eV)." Is this another DFT code reference or experiment?

If this is a comparison to experiment it would be good to check how close a DFT calculation actually gets to the observed L2/L3 edge results.

I noticed a few problems in your calculation:

• your calculation did not converge. Please increase NELM to at least 160. I needed 120 DAV steps to reach convergence
• consider to tightening the convergence criteria EDIFF to first produce more accurate wavefunctions
• you did non specify MAGMOM but doing a spin resolved calculation. Especially, with Fe in the compound this could influence the result electronic structure significantly.

Can you recheck those things? I will also ask around here if someone has another idea but to know better against what you compare your results would help.

And last but not least some advertisement for an upcoming workshop: https://www.vasp.at/info/post/workshop- ... t-2025-03/ that is explicitly on XAS and similar core related spectroscopy calculations with VASP.

Best,
Alex

[emmanuel_adejumo]

Hi Alex,

Thank you for your insights. The L2 (719.9 eV) and L3 (706.8 eV) energies refer to experimental binding energies, and I was comparing them with the results from my DFT calculations. I'll follow your suggestions to increase NELM to 160, tighten the EDIFF criteria, and include the MAGMOM settings for Fe to reflect its spin-polarized state.

I'll rerun the calculations and let you know how it goes.

Best regards,
Emmanuel