[Wannier] Dipole calculation

[giovanni.cistaro at uam.es]

Dear Wannier90 staff,
I am a PhD student at the Universidad Autónoma de Madrid, here is my  
question and I am currently using your code ouput as an input for my  
calculations.
I need to get the position operator matrix elements between Wannier  
functions and other functions I build up. In order to do it, I run a  
Wannier90 calculation and I set "wannier_plot = .true." with a big  
supercell, in order to know my wannier function in the real space.  
After reading the information from the .xsf file, I can calculate my  
integral.
I have a code that is able to calculate integral with functions like  
x*psi_1(x)*psi_2(x), and I already tested it with analytical  
functions. I also tried changing the coordinate system in the  
integral, since the wannier functions in the xsf file will be known in  
a system of coordinates that is different from the cartesian one.
I would like to test my code by reproducing the position operator  
matrix elements for wannier functions that I can read in the "_tb.dat"  
file.
For now I get very different results, so I wanted to ask some questions:
- Is the position operator defined only by the coordinate x? What I do  
is to translate it with respect to the origin given in the xsf file
- Is the program doing some rescaling on the wannier function, in  
order to plot it in a better way?
- What is the pole I should use to calculate the dipole moment, since  
it is well known that the dipole moment depends on the pole.

I know that the code doesn't calculate any integral to get the file  
"_tb.dat", but I think you could help me anyway!

Thank you
Giovanni