[Wien] Inconsistency in kgen

balabi balabi at qq.com
Tue Mar 19 08:09:38 CET 2024


Dear Prof. Peter Blaha,


I think I found another issue with kgen -1 mode especially concerned with I4/mmm symmetry.


As previously mentioned, the '-1' mode of kgen generates uneven k divisions, as you rightly pointed out. However, I've observed potential issues with the weight of the uneven k mesh, particularly in the context of I4/mmm symmetry (and possibly other symmetries as well). This discrepancy appears to lead to inaccuracies in determining the Fermi energy.


Here is how I benchmarked:


1. run_lapw -p  till converge for CaFe2As2 and 10 10 10 shift kmesh. save_lapw -d scf
2. x kgen generate 9 9 9 non shifted mesh | x lapw1 -p; x lapw2 -p -fermi | get Ef=0.5076760931
3. x kgen generate 9 9 13 non shifted mesh | x lapw1 -p; x lapw2 -p -fermi | get Ef=0.5028504280
2. x kgen -fbz generate full 9 9 9 non shifted mesh | x lapw1 -p; x lapw2 -p -fermi | get Ef=0.5076760047
3. x kgen -fbz generate full 9 9 13 non shifted mesh | x lapw1 -p; x lapw2 -p -fermi | get Ef=0.5077417577


You can observe the significant difference in the Ef obtained from the 9 9 13 kmesh in the irreducible Brillouin zone (IBZ). However, the Ef calculated from the full Brillouin zone (FBZ) using the same mesh appears normal. Consequently, I suspect there may be an issue with the weight of k-points in the 9 9 13 mesh generated by your modified kgen. On the other hand, equal division kmesh 9 9 9 gives consistent Ef for both ibz and fbz.


What is more, for 9 9 13 IBZ kmesh, when viewing fermi surface. xcrysden 1.6.2 gives error. xcrysden 1.5.60 gives completely wrong fermi surface. 


Please help, thank you very much!


best regards







 




------------------ Original ------------------
From:                                                                                                                        "A Mailing list for WIEN2k users"                                                                                    <peter.blaha at tuwien.ac.at>;
Date: Mon, Mar 11, 2024 08:33 PM
To: "wien"<wien at zeus.theochem.tuwien.ac.at>;

Subject: Re: [Wien] Inconsistency in kgen



Ups.
Here it comes.

Am 11.03.2024 um 13:26 schrieb balabi via Wien:
> Dear Prof. Peter Blaha
> 
> Thank you so much for your reply! But I can not find your attachment of 
> bravai.f.gz
> 
> best regards
> 
> ------------------------------------------------------------------------
> 
> 
> 
> ------------------ Original ------------------
> *From:* "A Mailing list for WIEN2k users" <peter.blaha at tuwien.ac.at>;
> *Date:* Mon, Mar 11, 2024 04:03 PM
> *To:* "wien"<wien at zeus.theochem.tuwien.ac.at>;
> *Subject:* Re: [Wien] Inconsistency in kgen
> 
> Hi,
> 
> Thank you very much for your report. I can confirm the problem.
> 
> Both, for bct and bco lattices (body-centered tetragonal or 
> orthorhombic) kgen enforced in default modes equal divisions of the 
> reciprocal lattice vectors (as it should be for bcc). This was not a 
> good choice and the selection made by option "-1" (mesh density in 
> bohr^-1) is correct.
> 
> I attach a modified   bravai.f.gz  file, which should be copied and 
> unziped in SRC_kgen, then recompiled (make; cp kgen ..).
> 
> PS: The prevous setting was not a problem if your k-mesh is converged 
> (besides the larger computational effort), but may lead to extra 
> inaccuracy for non-converged meshes.
> 
> Peter Blaha
> 
> Am 10.03.2024 um 14:48 schrieb 巴拉比 via Wien:
>> Dear wien2k developers and users,
>>
>> I am using wien2k 23.2 and working with CaFe2As2 structure which has 
>> I4/mmm symmetry. I am trying to generate klist using kgen. The kgen 
>> has several mode:
>>
>> the 1st mode is to specify k-mesh density
>>
>> /NUMBER OF K-POINTS IN WHOLE CELL: (0 for 3 divisions of K, -1 for 
>> delta-K)/
>> /-1/
>> / length of reciprocal lattice vectors (bohr^-1):  0.898   0.898   1.203/
>> /  Specify density of k-mesh in bohr^-1:/
>> /0.2/
>> /  Shift of k-mesh allowed. Do you want to shift: (0=no, 1=shift)/
>> /0/
>> /          17  k-points generated, ndiv=           5      5           7/
>> / delta-K (bohr^-1):     0.1796    0.1796    0.1719/
>> /KGEN ENDS/
>> /0.004u 0.016s 1:03.31 0.0%      0+0k 0+88io 0pf+0w/
>>
>> As you can see, the ndiv=5 5 7
>>
>> The 2nd mode is to specify number of k points
>>
>> /NUMBER OF K-POINTS IN WHOLE CELL: (0 for 3 divisions of K, -1 for 
>> delta-K)/
>> /1000/
>> / length of reciprocal lattice vectors (bohr^-1):  0.898   0.898   1.203/
>> /  Shift of k-mesh allowed. Do you want to shift: (0=no, 1=shift)/
>> /0/
>> /         102  k-points generated, ndiv=          10     10          10/
>> / delta-K (bohr^-1):     0.0898    0.0898    0.1203/
>> /KGEN ENDS/
>> /0.026u 0.003s 0:09.41 0.2%      0+0k 0+344io 0pf+0w/
>>
>> as you can see unlike -1 mode, the ndiv=10 10 10 which is even.
>>
>> The 3rd mode is to specify ndiv explicitly, and here comes the problem
>>
>> /NUMBER OF K-POINTS IN WHOLE CELL: (0 for 3 divisions of K, -1 for 
>> delta-K)/
>> /0/
>> / length of reciprocal lattice vectors (bohr^-1):  0.898   0.898   1.203/
>> /  Specify 3 mesh-divisions (n1,n2,n3):/
>> /5,5,7/
>> / Lattice symmetry requires equal mesh in x and z direction/
>> /  Specify 3 mesh-divisions (n1,n2,n3):/
>>
>> If I set ndiv as 5 5 7 as -1 mode. It just does not work. kgen insists 
>> equal mesh on x and z. So I must input even ndiv like 5 5 5.
>>
>> So the current issue is why the ndiv obtained with the -1 mode in kgen 
>> is not uniform for the CaFe2As2 system, whereas ndiv obtained with the 
>> k-point mode is uniform, and using the 0 mode, it's impossible to set 
>> non-uniform ndiv at all?
>>
>> finally, I am attaching the struct file of CaFe2As2 as below
>>
>> /blebleble /
>> /B   LATTICE,NONEQUIV.ATOMS:  3 139 I4/mmm /
>> /             RELA /
>> /  7.383336  7.383336 21.922849 90.000000 90.000000 90.000000/
>> /ATOM  -1: X=0.00000000 Y=0.00000000 Z=0.00000000/
>> /          MULT= 1          ISPLIT=-2/
>> /Ca1        NPT=  781  R0=0.00005000 RMT= 2.50000     Z: 20.0 /
>> /LOCAL ROT MATRIX:    1.0000000 0.0000000 0.0000000/
>> /                     0.0000000 1.0000000 0.0000000/
>> /                     0.0000000 0.0000000 1.0000000/
>> /ATOM  -2: X=0.50000000 Y=0.00000000 Z=0.25000000/
>> /          MULT= 2          ISPLIT=-2/
>> /      -2: X=0.00000000 Y=0.50000000 Z=0.25000000/
>> /Fe1        NPT=  781  R0=0.00005000 RMT= 2.28        Z: 26.0 /
>> /LOCAL ROT MATRIX:    0.7071068-0.7071068 0.0000000/
>> /                     0.7071068 0.7071068 0.0000000/
>> /                     0.0000000 0.0000000 1.0000000/
>> /ATOM  -3: X=0.00000000 Y=0.00000000 Z=0.63490625/
>> /          MULT= 2          ISPLIT=-2/
>> /      -3: X=0.00000000 Y=0.00000000 Z=0.36509375/
>> /As1        NPT=  781  R0=0.00005000 RMT= 2.17        Z: 33.0 /
>> /LOCAL ROT MATRIX:    1.0000000 0.0000000 0.0000000/
>> /                     0.0000000 1.0000000 0.0000000/
>> /                     0.0000000 0.0000000 1.0000000/
>> /  16      NUMBER OF SYMMETRY OPERATIONS/
>> / 1 0 0 0.00000000/
>> / 0 1 0 0.00000000/
>> / 0 0 1 0.00000000/
>> /       1/
>> /-1 0 0 0.00000000/
>> / 0-1 0 0.00000000/
>> / 0 0 1 0.00000000/
>> /       2/
>> / 0-1 0 0.00000000/
>> / 1 0 0 0.00000000/
>> / 0 0 1 0.00000000/
>> /       3/
>> / 0 1 0 0.00000000/
>> /-1 0 0 0.00000000/
>> / 0 0 1 0.00000000/
>> /       4/
>> /-1 0 0 0.00000000/
>> / 0 1 0 0.00000000/
>> / 0 0-1 0.00000000/
>> /       5/
>> / 1 0 0 0.00000000/
>> / 0-1 0 0.00000000/
>> / 0 0-1 0.00000000/
>> /       6/
>> / 0 1 0 0.00000000/
>> / 1 0 0 0.00000000/
>> / 0 0-1 0.00000000/
>> /       7/
>> / 0-1 0 0.00000000/
>> /-1 0 0 0.00000000/
>> / 0 0-1 0.00000000/
>> /       8/
>> /-1 0 0 0.00000000/
>> / 0-1 0 0.00000000/
>> / 0 0-1 0.00000000/
>> /       9/
>> / 1 0 0 0.00000000/
>> / 0 1 0 0.00000000/
>> / 0 0-1 0.00000000/
>> /      10/
>> / 0 1 0 0.00000000/
>> /-1 0 0 0.00000000/
>> / 0 0-1 0.00000000/
>> /      11/
>> / 0-1 0 0.00000000/
>> / 1 0 0 0.00000000/
>> / 0 0-1 0.00000000/
>> /      12/
>> / 1 0 0 0.00000000/
>> / 0-1 0 0.00000000/
>> / 0 0 1 0.00000000/
>> /      13/
>> /-1 0 0 0.00000000/
>> / 0 1 0 0.00000000/
>> / 0 0 1 0.00000000/
>> /      14/
>> / 0-1 0 0.00000000/
>> /-1 0 0 0.00000000/
>> / 0 0 1 0.00000000/
>> /      15/
>> / 0 1 0 0.00000000/
>> / 1 0 0 0.00000000/
>> / 0 0 1 0.00000000/
>> /      16/
>>
>>
>> best regards
>> ------------------------------------------------------------------------
>>
>> _______________________________________________
>> Wien mailing list
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> 
> -- 
> -----------------------------------------------------------------------
> Peter Blaha,  Inst. f. Materials Chemistry, TU Vienna, A-1060 Vienna
> Phone: +43-158801165300
> Email:peter.blaha at tuwien.ac.at           
> WWW:http://www.imc.tuwien.ac.at       WIEN2k:http://www.wien2k.at
> -------------------------------------------------------------------------
> 
> 
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-- 
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Phone: +43-1-58801-165300
Email: peter.blaha at tuwien.ac.at    WIEN2k: http://www.wien2k.at
WWW:   http://www.imc.tuwien.ac.at
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