#1 Mossbauer parameters by Zhiwei Li 24.04.2021 08:27

Dear fleur developers,

It would be very interesting if we can calculate Mossbauer parameters, isomer shift, electric field gradient, and hyperfine field(with different contributions output separately, contact field+orbital+dipole field).

Best,
Zhiwei

#2 RE: Mossbauer parameters by Gregor 29.04.2021 10:06

In future Fleur development user demanded functionalities will become more important. Therefore it is very helpful for us to get user feedback on such wishes. Thank you for making us aware of the Mössbauer parameters. We will definitly investigate if and how we can implement their calculation. But please be aware that this is nothing we can deliver within a few weeks.

#3 Status check by Zhiwei Li 13.05.2022 09:29

Dear fleur developers,

It's been a year since my last check, I just want to see what is the status now? Is there anyone working on this problem?

Thanks for your wonderful work!

Zhiwei

#4 RE: Status check by Gregor 17.05.2022 13:15

Dear Zhiwei,

I start to investigate this right now. I hope I find enough time to implement it.

Is my understanding correct that you need output for

1. isomer shift
2. quadrupole splitting
3. magnetic hyperfine field

Could you clarify on whether I am missing something or you only need a subset of these quantities?

You mentioned that you also need the electric field gradient?

Best, Gregor.

#5 RE: Status check by Zhiwei Li 18.05.2022 10:04

Dear Gregor,

Thank you for putting this into fleur. We do need the following three parts:
1) The isomer shift, in fact this is related to the s-electron density (Isomer shift = a * density) at the nucleus and the proportion constant, a, is materials relevant. Therefore, the output should be just the corresponding s-electron density I think.
2) The quadrupole splitting is related to the electric field gradient. In this case, the electric field gradient is enough.
3) the magnetic hyperfine field.

In understanding the calculated numbers, it is good to know different contributions to these quantities. Therefore, it would be nice that the output contains the total results and also how much contributions from different physical orgins.

Best,
Zhiwei

#6 Zhiwei Li by Zhiwei Li 18.05.2022 14:17

Dear Gregor,

I found these notes from wien2k website which might be helpful. There, they have some notes on how they implemented the calculations of EFG and hyperfine field.
ww.wien2k.at/reg_user/textbooks/

Also these papers might help
journals.aps.org/prb/abstract/10.1103/PhysRevB.35.3271
journals.aps.org/prb/abstract/10.1103/PhysRevB.81.174412

best,
Zhiwei

#7 RE: Zhiwei Li by Gregor 20.05.2022 19:23

With respect to the papers: We actually have code to calculate hyperfine fields in the code. It is employed by using a different core electron solver, which is done by setting the input parameter kcrel to 1. But this code is rarely used I thus have to check whether it is still correct. ...I will also beautify the output. The other Mössbauer parameters are probably not yet calculated by the code.

At the moment the output for the hyperfine fields is shell-resolved, i.e., one obtains contributions from 1s, 2s, 2p, 3s, 3p and so on. Does such an output fit your needs?

#8 Zhiwei Li by Zhiwei Li 09.06.2022 14:16

Dear Gregor,

Sorry for this late reply.

Thank you very much for this good news. The shell-resolved output should be fine I think.

one more thing, please can you write a short explanation on how to use this feature, because I could find any tutorial on this subject on the website of fleur.
For example, make a short example on some simple systems from which we can learn how to calculate these parameters that we measure with experiments.

Best,
Zhiwei

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