[Wannier] Discrepancy in Z₂ Invariant Results for Bi₂Se₃ Using WannierTools
Poonam Sharma
poonamsharma at iiserb.ac.in
Tue Jun 10 20:08:13 CEST 2025
Dear All,
I have performed Z₂ invariant calculations for Bi₂Se₃ using
WannierTools (with VASP). For reference, I followed the example
provided in the official documentation:
https://wannier-tools.readthedocs.io/en/latest/tutorials/Bi2Se3.html
In that example, the Z₂ invariants for the six time-reversal invariant
momentum (TRIM) planes are reported as:
k₁ = 0.0, k₂-k₃ plane: z₂ = 1
k₁ = 0.5, k₂-k₃ plane: z₂ = 0
k₂ = 0.0, k₁-k₃ plane: z₂ = 1
k₂ = 0.5, k₁-k₃ plane: z₂ = 0
k₃ = 0.0, k₁-k₂ plane: z₂ = 1
k₃ = 0.5, k₁-k₂ plane: z₂ = 0
However, in my case, using the same POSCAR file from the tutorial
(https://github.com/quanshengwu/wannier_tools) and following the same
procedure, I obtained:
k₁ = 0.0, k₂-k₃ plane: z₂ = 1
k₁ = 0.5, k₂-k₃ plane: z₂ = 0
k₂ = 0.0, k₁-k₃ plane: z₂ = 1
k₂ = 0.5, k₁-k₃ plane: z₂ = 0
k₃ = 0.0, k₁-k₂ plane: z₂ = 0
k₃ = 0.5, k₁-k₂ plane: z₂ = 1
So, for the k₃ direction, my results are exactly the opposite of those
reported in the example.
Here is my POSCAR file:
Bi2Se3
1.0
-2.069 -3.583614 0.000000
2.069 -3.583614 0.000000
0.000 2.389075 9.546667
Bi Se
2 3
Direct
0.3990 0.3990 0.6970
0.6010 0.6010 0.3030
0 0 0.5
0.2060 0.2060 0.1180
0.7940 0.7940 0.8820
I'm unable to figure out why this discrepancy is occurring. I am using
VASP.6.4.3, and my projection part is coming completely fine (perfect
overlapping).
Also, when I am using the provided wannier90_hr.dat file and
calculated the Z₂ values, it is coming correct with VASP.6.4.3. I am
new to these calculations, please suggest as I am not getting why this
is happening. If my output files are required, plet let me know.
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