How to set a correspondingly correct q vector with the document

FLEUR Forum � User support � Magnetism, Non-collinear calculations, SOC � How to set a correspondingly correct q vector with the document

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#1 | How to set a correspondingly correct q vector with the document datum

Wed Feb 21, 2024 2:43 pm

I want to reproduce figure 2 of paper PHYSICAL REVIEW B 66, 014447(2002) that is about spin spiral calculation of fcc gamma iron. Now the problem I encounter is that if I directly input the q vector path in the document respectively, eg. (0,0,1),(0,0,0.1), the curve I got(I have tested a=6.82) had a totally different tendency with the document. I have tried lots of sets of parameters, but the trend remains almost the same. What specific q vector should I set? Am I on the right way to solve this problem? I would appreciate it if you could help me with this issue.

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#2 | RE: How to set a correspondingly correct q vector with the document datum

Fri Feb 23, 2024 5:31 pm

Dear Yule,

Could you please attach an out.xml file (you might have to add a .txt suffix) so that I can better understand what is happening!?

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#3 | supplementary information datum

Sat Feb 24, 2024 4:38 pm

Unfortunately, I can't upload those xml files even if I have copied them into txt files and then uploaded. If you want to know part of out.xml files, I can post them to you in this texting part. I am sorry for this problem.
Sincerely,
Yule

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#4 | A further clarification datum

Mon Feb 26, 2024 4:04 pm

I am intended to further clarify me questions. Actually, as what I mentioned, I directly input(0,0,1) into the software to represent X point q vector of gamma iron, because the document said that q=2pai/a(0,0,1) at X point. However, today I saw one similar post on this forum which said that 'Then I define the q vector = (0.0, -0.8469595, 1.42649607), which will describe a spin spiral in z-direction [reciprocal lattice * q = (0,0,1)]'. Thus, I am curious about what I should set for my desired q vector in this software. Could you please provide me a general guide for q vector setting? I would appreciate it if you could help me.
Sincerely,
Yule

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#5 | Another confusing point datum

Wed Feb 28, 2024 7:26 am

Dear Gregor,
I found that on FLEUR website, it depicts fcc gamma iron FM state as q vector(0,0,0), and AFM as (0.5,0.5,0). However, all paper I have seen set q vector from(0,0,0) to （0，0，1). (Spin spiral ground state of g -iron ,K. Kno¨pfle, L. M. Sandratskii, and J. Ku¨bler) What's the reason? According to my test, these two ways gain totally different tendency.
Best,
Yule

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#6 | RE: Another confusing point datum

Fri Mar 01, 2024 9:15 am

Dear Yule,

Discrepancies in the definition of q points and the spin-spiral dispersion relation can stem from 3 causes...

1. It may be a matter of the coordinate system in which the respective code expects the q-points to be provided. In FLEUR we expect the q-vector in terms of reciprocal lattice vectors. Other codes may expect them in terms of cartesian coordinates. If you multiply the vector (0.5,0.5,0) with the reciprocal Bravais matrix you obtain a vector that is only in the z-component nonzero. You then have the q-vector in cartesian coordinates. As said, it may be that some other code or some specification in the literature uses cartesian coordinates.

2. The unit cell of your system may be specified in different ways, which then also affects the reciprocal Bravais matrix. The q-vector of (0.5,0.5,0.0) is related to the common specification of the primitive unit cell of an fcc crystal. This, of course, is not unique. You can also specify other primitive unit cells for fcc crystals and you may also work with a conventional unit cell containing more atoms.

3. I was asking about the output file, because in versions 6.x of FLEUR we had a bug that affected the spin-spiral dispersion if you also have local orbitals as part of the used basis set. If that is the case I would suggest to use the newest development version of the code. Please check whether these two conditions - version MaX 6.x of the code and local orbitals - may be a cause for the discrepancy.

Best, Gregor.

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#7 | problem gets solved datum

Sat Mar 02, 2024 9:13 am

Dear Gregor,
Thank you for your help. The problem was solved with your help.
Sincerely,
Yule

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