f-electrons treatment in AkaiKKR

Posted on : June 26, 2022 (Sun) 03:48:18

by ibrahim

Dear all,

I am working on the ThMn12 phases that contains both Nd and Ce rare-earth elements. After I read several papers, which authors also benefited AkaiKKR I am a bit confused. Here I report two statements.

1. arXiv:1901.10119v1 --> "We set lmax = 3 putting all 4f electrons in the valence state. This should be the proper description for La and Ce4+ as found in the 4f-3d intermetallics containing ferromagnetic Fe."

2. DOI: 10.1103/PhysRevMaterials.5.013806 --> "We set lmax = 2 putting all 4 f electrons of the valence state on the basis of open-core approximation. We assume each configuration of the electrons as Nd3+, Pr3+, and Ce4+,"

Although both papers have common authors, in the first paper they set lmax=3 to put f-electrons in the valence and in the second they set lmax=3.

So my question is in general how to treat the f-electrons in AkaiKKR? I mean Nd+3 would be the correct treatment, it has strongly localized f-electrons and open core treatment must be applied. In the case of Ce, it has hybridization with Fe 3d-electrons. Perhaps, f-in core treatment would give a better result.

For both cases what would be the proper lmax parameter?

I will be appreciated if you can give some feedback for my confusion.

Regards

[Re:01] f-electrons treatment in AkaiKKR

Posted on : February 15, 2023 (Wed) 19:46:29

by Vitaliy

Normally, one treats RE elements with f-electrons as core states. That means lmax=2. If you treat them with lmax=3, then f-states will appear almost at the Fermi level which wrong and is a common problem for f-elements and DFT. In this case one needs to use other code where DFT-U (Hubbard U correction) is implemented (some FLAPW codes: Wien2k, Elk, exciting, etc.). There, you can artificially split f-states into higher and lower energies. But bear in mind that for the light rare earths this is a tricky task.