[Wannier] bandstructure of graphene/h-BN

[Aron Szabo]

Try to use an odd mesh, like 19x19x1 or 21x21x1. Sometimes it matters a 
lot whether you include the Gamma point or not. But it is just a guess, 
I don't know for sure why you get these results. It could also be that 
the wavefunctions were not converged in the second case. Did you run 
first a self-consistent simulation then a second one with NELM set to 0 
to generate the projections? Or did you do everything in one step in the 
second simulation too (like in the INCAR file you've attached?)? Because 
in the first case it is possible that VASP could not read in the WAVECAR 
correctly. Sometimes it does not even give a warning, and tells that it 
had read the WAVECAR, but still it starts from non-converged 
wavefunctions, and I don't know exactly why. One possible cause is that 
the NPAR or KPAR parameters were changed between the two runs, but 
sometimes even with the same setting it does not work. So you should 
check the eigenvalues of the VASP run whether they make sense. And I 
usually also set the LORBIT=10 to project the VASP wavefunctions to 
atomic orbitals (independently of Wannier90), and see if the bands I'm 
interested in really have the character I expected.
Also, don't set use_bloch_phases=T if you explicitly set the projections.

Best,
Aron

On 09/20/2015 01:48 PM, 徐金荣 同济大学 wrote:
> Dear Wannier90's users and developers:
>         Recently, I have been  fitting  the bandstructure of bilayer 
> graphene/h-BN using vasp2wannier90 code.  The bandstructure below 
> (figure1) is similar to DFT result's when I use fewer Kpoints (eg. 
> KPOINTS: 5*5*1).
> ,
> figure 1
>
>
> calculated file as below:
> *INCAR*
> step3:GW calculation
> ALGO = GW0 ; LSPECTRAL = .TRUE. ; NOMEGA = 60
> NBANDS=72
> #LRPA = .FALSE.
> LWANNIER90=.TRUE.
> *KPOINTS*
> Automatic mesh
> 0
> G
> 5 5 1
> *POSCAR*
> grephene-BN 1*1*1
> 1.0
> 2.1304224933097191    -1.23           0.0
> 0.0     2.46           0.0
> 0.0     0.0           20.52
> 2 1 1
> d
> 0.0000000000000000  -0.0000000000000000  0.5833333333333333
> 0.3333333333333333  0.6666666666666667   0.5833333333333333
> 0.0000000000000000  -0.0000000000000000  0.4166666666666667
> 0.6666666666666667  0.3333333333333333   0.4166666666666667
> *Wannier90.win*
>  num_wann =    12  ! set to NBANDS by VASP
>  num_bands=    24
> exclude_bands: 25-72
>
> Begin Projections
> #C:sp2;pz
> #C:l=1,mr=1
> #B:l=1,mr=1
> #N:l=1,mr=1
> #C:sp2;pz
> #B:sp2;pz
> #N:sp2;pz
> C:l=1
> B:l=1
> N:l=1
> End Projections
>
> #dis_froz_max=9
> dis_num_iter=1000
>
> guiding_centres=true
>
>
> use_bloch_phases = T
>
> begin unit_cell_cart
>    2.1304225    -1.2300000     0.0000000
>    0.0000000     2.4600000     0.0000000
>    0.0000000     0.0000000    20.5200000
> end unit_cell_cart
>
> begin atoms_cart
> C        0.0000000     0.0000000    11.9700000
> C        0.7101408     1.2300000    11.9700000
> B        0.0000000     0.0000000     8.5500000
> N        1.4202817     0.0000000     8.5500000
> end atoms_cart
>
> mp_grid =     5     5     1
>
>
>
>
>
> But when I increase Kpoints to 20*20*1 in order to get high-quality 
> results, I get wrong results (figure2)
> The calculated files are as below:
> *INCAR*
> step3:GW calculation
> ALGO = GW0 ; LSPECTRAL = .TRUE. ; NOMEGA = 120
> NBANDS=72
> #LRPA = .FALSE.
> LWANNIER90=.TRUE.
> *KPOINTS*
> Automatic mesh
> 0
> G
> 20 20 1
>
> Why the results are wrong? How should I adjust the parameters?
>
> I look forward to receive your reply.
>
> Thanking you and with regards.
> Kinglong Xu.
>
>
>
>
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> Wannier at quantum-espresso.org
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