[Wannier] Extracting the tight-binding elements from Wannier90

[Alex.Durie]

Dear all,


Forgive the nature of this question, as I know there has been much previous discussion. I am new to Wannier90 and wish to extract the tight-binding parameters to use within my existing C++ code. I am attempting to compare against results that I have obtained using potentials within 'The Handbook of the Bandstructure of Elemental Solids' by D. Papaconstantopoulos.


I thought a good place to start would be bcc Fe spin up. To that end, I have started with input files from example08 with the following additions;


write_hr = true
use_ws_distance = true
bands_plot_mode = cut
dist_cutoff = 5

as I was hoping to use up to second nearest neighbour interactions, and wanted to check the bandstructure was sufficiently accurate.


I have attempted to use the relevant data within seedname_hr.dat to reconstruct the bandstructure in my C++ code to make sure I was building the Hamiltonians correctly and seem to be running into difficulty.


I assumed these were the lines of seedname_hr.dat that were relevant;


    0    0    0    n    m   real    imag
    1    1    1    n    m   real    imag
   -1    1    1    n    m   real    imag
    1   -1    1    n    m   real    imag
    1    1   -1    n    m   real    imag
   -1   -1    1    n    m   real    imag
    1   -1   -1    n    m   real    imag
   -1    1   -1    n    m   real    imag
   -1   -1   -1    n    m   real    imag
    2    0    0    n    m   real    imag
   -2    0    0    n    m   real    imag
    0    2    0    n    m   real    imag
    0   -2    0    n    m   real    imag
    0    0    2    n    m   real    imag
    0    0   -2    n    m   real    imag

but using these values does not yield the same bandstructure as that in iron_up_band.gnu.
Is there some form of reordering required that I have not considered?
Also, at R = 0,0,0 I am getting non-zero off-diagonal elements. Is that an error in output?

Also, I would have expected dist_cutoff = 2.942225 to be suitable to calculate the bandstructure up to second nearest-neighbour, but found that I needed dist_cutoff = 5 to observe non-zero second nearest-neighbour terms in iron_up.wout, under
     "Maximum absolute value of Real-space Hamiltonian at each lattice point"
unless I am misinterpreting the information?

Thanks in advance to anyone who can put me on the right track.

Alex Durie
PhD student
The Open University
United Kingdom
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