### [QE-users] 回复: Effective mass and the unit of k

Thank you very much for solving my confusion. I'm really using a Cartesian
coordinate system. Thank you!!!

shenjiale...@outlook.com

Dear Jiale Shen
If i understand your question correctly you are asking why the following
k-point values neither matches 1/A nor 2*pi/A. ?
k-vaspkit k-vasprun.xml k-QE 1/A 2pi/A ? 0 0 0 0.019 0.00302 0.0174 0.038
0.00605 0.0347 0.05699 0.00907 0.0521 0.07599 0.01209 0.0694 0.09499 0.01512
0.0868 0.11399 0.01814 0.1042 0.13299 0.02117 0.1215 0.15198 0.02419 0.1389
0.17098 0.02721 0.1562 0.18998 0.03024 0.1736 0.20898 0.03326 0.191 0.22798
0.03628 0.2083 0.24697 0.03931 0.2257 0.26597 0.04233 0.243.
check your  scf input file whether atom positions are given in cartesian
coordinates. If this is correct then what you have here in the 3rd column is
the magnitude of the k-vector given in 1/A units and not necessarily the same
as your first column. If you have used the atom positions of both VASP and QE
using the same units then these k-points will match.

Regards
Ramesh Kumar
Assistant Professor
GITAM University, India

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### [QE-users] 回复: Effective mass and the unit of k

Thanks for your reply! But I’m still confused about the unit of k, and I
compared two systems, one Si and the other my structure. The band calculations
were performed with VASP and QE respectively, and the exported data classified
and sorted out. For the convenience of presentation, I only copied the first 15
data points here. The first column below is the k value in BAND.dat that I
output through vaspkit program, the second column is the k value in the
exported data through the analysis of vasprun.xml by p4vasp, and the third
column is the k value of the exported data through the bands. x module of
qe6.6. The unit of vaspkit output k is known to be 1/A, and the unit of
vasprun.xml is 2pi/A. The two units of qe output confuse me, for the Si system,
I think the unit is 1/Bohr, whereas in the other system it is obviously not
1/Bohr. Why are the data output by QE's bands.x so different in unit?

Si system
k-vaspkit  k-vasprun.xmlk-QE
1/A   2pi/A  ?
0   00
0.061210.00974  0.0354
0.122410.01948  0.0707
0.18362 0.02922 0.1061
0.244820.03896  0.1414
0.30603 0.04871 0.1768
0.36723 0.05845 0.2121
0.42844 0.06819 0.2475
0.48964 0.07793 0.2828
0.55085 0.08767 0.3182
0.61206 0.09741 0.3536
0.67326 0.10715 0.3889
0.73447 0.11689 0.4243
0.79567 0.12664 0.4596
0.85688 0.13638 0.495

My system
k-vaspkit  k-vasprun.xmlk-QE
1/A   2pi/A ?
0   00
0.0190.00302  0.0174
0.0380.00605  0.0347
0.056990.00907  0.0521
0.075990.01209  0.0694
0.094990.01512  0.0868
0.113990.01814  0.1042
0.132990.02117  0.1215
0.151980.02419  0.1389
0.170980.02721  0.1562
0.189980.03024  0.1736
0.208980.03326  0.191
0.227980.03628  0.2083
0.246970.03931  0.2257
0.265970.04233  0.243

--
Best Regards
Jiale Shen
Ph.D. Student
Beijing Institute of Technology

Usually k-points in band plots are in 2\pi/a units

On 23/03/2023 18:54, jiale shen wrote:
>
> You don't often get email from shenjiale...@outlook.com. Learn why this
> is important
>
>
> Dear QE users:
>
> I want to fit the bandstructure data calculated by qe6.6 to obtain the
> effective mass. We used the bands. x module to obtain the band.dat.gnu.
> What is the unit of the first column k? For example, the first column
> unit given by vaspkit is 1/A. Does anyone know the exact unit of the
> first column obtained by bands. x? "CELL_PARAMETERS (angstrom)" set in
> my input file.Any procedure on QE calculate the effective mass of 3D
> system?**
>
> --
>
>
> Best Regards
> Jiale Shen
> Ph.D. Student**
>
> Beijing Institute of Technology
>
> 从Windows 版邮件
>
>
> ___
> The Quantum ESPRESSO community stands by the Ukrainian
> people and expresses its concerns about the devastating
> effects that the Russian military offensive has on their
> country and on the free and peaceful scientific, cultural,
> and economic cooperation amongst peoples
> ___
> Quantum ESPRESSO is supported by MaX
> (www.max-centre.eu)
> users mailing list users@lists.quantum-espresso.org
> https://lists.quantum-espresso.org/mailman/listinfo/users

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Univ. Udine, via delle Scienze 206, 33100 Udine Italy, +39-0432-558216

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