unphysical ELF for NdNiO2

[foyevtsova]

Hello,

I want to calculate electron localization function for the novel infinite-layer nickelate NdNiO2. The result seems unphysical: the ELF is very low around Ni atoms where one expects it to be rather high because of the strongly localized 3d electrons. At the same time Quantum Espresso gives a physically reasonalbe picture, please, check the figure below.

Thank you,
Kateryna Foyevtsova

[andreas.singraber]

Hello Kateryna Foyevtsova!

Thank you for your report! My colleagues and I had a look at the problem and indeed we also found the behavior very unreasonable. All other VASP output strongly indicates localized 3d electrons around Ni but somehow the ELF calculation does not account for that. I will have a closer look and report back when I have an explanation.

All the best,

Andreas Singraber

[marie-therese.huebsch]

Dear Kateryna,

We looked into the problem and found that the current implementation depends strongly on the choice of the POTCAR. You can test this by using the GW POTCAR and will find contributions from Ni 3d electrons. We believe that with this pseudo-potential dependent ELF is not a good measure for electronic localisation and thus want to replace this (very old) implementation in a future release.

In the meantime, let me stress that the underlying Kohn-Sham orbitals are fine. You can see the Ni 3d character in the PROCAR file. I hope that the current issue does not cause too much inconvenience in your research project. Does it suffice for you to have the orbital character? Or do you perhaps want to look at partial charge densities or Wannier functions to gain inside about the localisation? There are many features that might help answer the scientific question you are posing.

Best regards,
Marie-Therese

[foyevtsova]

Dear Marie-Therese,

thank you very much for taking time to investigate this issue and to reply. As per your advice, I will resort to other ways of analysing electron localization in this material. I am looking forward to having a chance to appy the new VASP implementation of ELF.

Best regards,
Kateryna

[marie-therese.huebsch]

Thank you very much for understanding! We will continue to work on improving VASP.