[Wannier] Berry connection from Wannier functions

[giovanni.cistaro at uam.es]

Hello,
I'm trying to use Wannier90 in order to calculate the Berry connection  
in graphene (in the wannier basis) starting from eq. 23 in the paper  
"Maximally localized Wannier functions: Theory and applications" by  
Marzary et al, Rev. of Mod. Phys., 84.
I got stuck when I found that the Berry connection calculated from my  
_tb.dat file is not hermitian.
I found out that this is related to the output of wannier90: one  
expect that in order for the Berry connection to be Hermitian the  
position operator in the wannier basis has to satisfy the property:

<0 m|r|R n> = <0 n|r|-R m>*

but the matrix elements that I can see in my file don't satisfy this property.
I was wondering if you are aware of this problem and you know how to solve it.

Looking at the wout file, I found out that the wannier functions |0n>  
are not centered at the R=0 unit cell. Can this be the problem? How  
can I impose the centre of the wannier functions?
I attach my _tb.dat and .wout files.
Thank you
Giovanni Consalvo Cistaro
PhD at Universidad Autónoma de Madrid

-------------- next part --------------
An embedded and charset-unspecified text was scrubbed...
Name: graphene_tb.dat
URL: <http://lists.quantum-espresso.org/pipermail/wannier/attachments/20191108/7602d4ee/attachment-0002.ksh>
-------------- next part --------------
An embedded and charset-unspecified text was scrubbed...
Name: graphene.wout
URL: <http://lists.quantum-espresso.org/pipermail/wannier/attachments/20191108/7602d4ee/attachment-0003.ksh>