[Wannier] Problem with disentanglement

[Mostofi, Arash]

Dear Christoph,

The input parameter num_bands should be equal to the number of rows/columns in the overlap matrix M_{mn}(k,b) matrix that is fed into Wannier90. In the case of the 5 isolated d-orbitals, presumably you set

exclude_bands = 6-44

then computed the 5x5 M matrix at each (k,b), and used num_wann=5 (and num_bands=5). Here there is no disentanglement as you are computing 5 WFs from 5 isolated bands.

Now that you want to wannierise the other bands, you need the full M matrix (or at least with only bands 1-5 excluded, for example). So you need to recalculate M, and set num_bands appropriately. Then you’ll have something like num_wann=12, num_bands=44 (if you’ve not excluded the d states), and the code will try to disentangle and wannierise.

Hope this helps,

Arash

—
Arash Mostofi — www.mostofigroup.org<http://www.mostofigroup.org>
Director, Thomas Young Centre @Imperial
Imperial College London



On 27 Mar 2017, at 16:27, Christoph Wolf(신소재공학과) <chwolf at postech.ac.kr<mailto:chwolf at postech.ac.kr>> wrote:

Dear all!

I am facing some problems with disentanglement using QE6.0

My system is a cubic perovskite CsPbBr3. I calculated nscf with 44 bands (22 valence and equal number of unoccupied bands). I first calculated the pdos to identify the contributions of orbitals to the bands (fatband representation); the output is as below:

<image003.png>
Here, I chose Pb(6s,6p)+Br(4p).
As test-case I calculate the MLWF of the Pb d-band (located below -12 eV) excluding all bands 6-44

The resulting MLWF look nicely like   d-orbitals so I think it is all right there. Now I want to get the same for the bands shown above; as they are not separated well I want to take the “disentanglement approach” but I think I am doing it wrong;

Using this as input:

num_wann  12
num_bands 12

begin projections
Pb:p !1x3=3
Br:p ! 3x3=9
end projections

dis_win_min -15.000
dis_win_max  15.000
dis_froz_min -2.000
dis_froz_max  5.000

I unfortunately get

Wanted band  : 1 found band  : 13
Wanted kpoint: 2 found kpoint: 1
A common cause of this error is using the wrong
number of bands. Check your input files.
If your pseudopotentials have shallow core states remember
to account for these electrons.

Now I tried to move the frozen window a bit but that didn’t change; I also tried to exclude other bands by the exclude_bands keyword excluding all but the above but it didn’t work either.

I am relatively new to wannier90 so I appreciate any help!

Thank you in advance!

Chris

Materials Science and Engineering
POSTECH university, Korea

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