[Wien] Inconsistency in kgen

[Peter Blaha]

Hi,
No, you should not modify the kmesh.
The k-vectors are generated in the primitive (non-orthogonal) basis, but 
transformed afterwards to carthesian coordinates.
By this operation, some of the k-points may obtain values larger than one.
Note, that in carthesian coordinates, the BZ does not go from 0-1 in 
kx,ky,kz.
You also noted that (0,0,0) yields different eigenvalues than (1,1,1).


Am 21.03.2024 um 04:39 schrieb balabi via Wien:
> Dear Prof. Peter Blaha,
> 
> Thank you very much for your new fix.
> 
> I have another question. When we generate an fbz 10x10x10 non-shifted 
> kmesh for CaFe2As2, the klist file contains 1000 points. However, many 
> of these points fall outside the 10x10x10 range. For example, the 560th 
> point is listed as "14 14 10".
> 
> I guess applying the modulo operation by 10 is necessary, so "14 14 10" 
> would be equivalent to "4 4 0," correct? However, when I apply modulo to 
> all k-points, I find that many k-points are missing (e.g., {0,0,1}, 
> {0,0,3}) and duplicated (in terms of modulo).
> 
> Why is this happening? In the context of the FBZ, shouldn't the klist 
> file contain 1000 unique k-points?
> 
> Specifically, the 556th k-point is "10 10 10," which should be 
> equivalent to "0 0 0" according to modulo. However, I checked the "0 0 
> 0" k-point in output1 file has different eigenvalues compared to the 
> 556th "10 10 10" k-point. I am confused by this discrepancy. Which k 
> point "10 10 10" really refers? Please help. Thank you very much.
> 
> Best regards,
> 
> 
> ------------------ Original ------------------
> *From:* "A Mailing list for WIEN2k users" <peter.blaha at tuwien.ac.at>;
> *Date:* Wed, Mar 20, 2024 05:48 AM
> *To:* "wien"<wien at zeus.theochem.tuwien.ac.at>;
> *Subject:* Re: [Wien] Inconsistency in kgen
> 
> Hi,
> 
> Yes, my fix was not correct. The bct and bco lattices are special cases
> and are also discussed in literature.
> 
> While the direct lattice vectors in bct have all the same length, the
> reciprocal lattice is face-centered tetragonal and thus they have
> different length. Nevertheless as far as I understand it is usually
> recommended to use the same divisions of them, when constructing a
> k-mesh. This was also enforced in WIEN2k, only the recent addition of
> specifying a delta-k was breaking this, but led to wrong multiplicities.
> The algorithm for finding the multiplicity does not work for bct, when
> the divisions are not the same.
> 
> The present fix is to go back to the original bravai.f and use the new
> basdiv.f, which enforces equal k-divisions in the bct/bco case.
> 
> 
> Thanks for checking.
> 
> Peter Blaha
> 
> 
> 
> 
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-- 
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-165300
Email: peter.blaha at tuwien.ac.at    WIEN2k: http://www.wien2k.at
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