Thank you so much for all the suggestions. Dear Matt, thank you for pointing out my rookie mistake and suggested correction. I didn't consider J-T distortion in my new try but the fitting was improved nonetheless. You suggested changing dk from 1 to 4 or 5 for the Kaiser-Bessel window and this has been proved helpful. I guess some appreciation of how the windows function works is needed to really gain insight into why the change of dk is beneficial to the fitting. Also, I was wondering if you can suggest dk values for other windows?

Dear Matthew, thank you for your suggestion about using the two shell model. Just like you and Matt pointed out, limited k range poses a great challenge in analyzing J-T distortion. At this point, I do not have enough confidence to implement two shell model.

Dear Dominik, thank you for your recommendation of the paper. I looked through it and found that a combination of diagnostic tools was used in that paper. The J-T distortion analysis was based on the results of both XAS and vibrational spectroscopy.

Dear Ditty, thank you for your suggestion also. I attached the new fitting file along with the LiCoO3 inp file that you may need.

In the new fitting, I actually input the LiMnO2 file (with the same structure as previous LiCoO3) as the sample is more like Fe-doped LiMnO3 (though there're actually substantial doped Ni present and I don't know how to consider that yet).