[Wannier] Reciprocal vectors in wannier90 vs Quantum espresso

[Youssef Aharbil]

Dear All,

I have noticed that the reciprocal vectors computed via wannnier90 and
quantum espresso (QE) are different***, which means that the Kpath and
segment length across the BZ aren't the some for both code though handling
the same crystal structure.



In order to investigate this issue, I have dug inside the source code of
wannier90 and QE and compared the formula used in each code and finally
realized the root cause, In fact QE divide the reciprocal vectors by an
additional term, the real space vector denominator (den variable in
recips.f90), which isn't the case for wannier90 (utility.F90).

So, I am really confused, I can manually fix this, but I wanted to share
with you.
Any suggestions or clues are most welcome.


***
Wannier90 header:

                                    ------
                                    SYSTEM
                                    ------

                              Lattice Vectors (Ang)
                    a_1     2.784694  -1.607742   4.581610
                    a_2     0.000000   3.215484   4.581610
                    a_3    -2.784694  -1.607742   4.581610

                   Unit Cell Volume:     123.07314  (Ang^3)

                        Reciprocal-Space Vectors (Ang^-1)
                    b_1     1.128164  -0.651347   0.457131
                    b_2     0.000000   1.302693   0.457131
                    b_3    -1.128164  -0.651347   0.457131


QE Header:

     celldm(1)=  10.577485  celldm(2)=   0.000000  celldm(3)=   0.000000
     celldm(4)=   0.504986  celldm(5)=   0.000000  celldm(6)=   0.000000

     crystal axes: (cart. coord. in units of alat)
               a(1) = (   0.497501  -0.287232   0.818530 )
               a(2) = (   0.000000   0.574464   0.818530 )
               a(3) = (  -0.497501  -0.287232   0.818530 )

     reciprocal axes: (cart. coord. in units 2 pi/alat)
               b(1) = (  1.005024 -0.580251  0.407234 )
               b(2) = (  0.000000  1.160501  0.407234 )
               b(3) = ( -1.005024 -0.580251  0.407234 )


Youssef Aharbil,
Laboratory of Physics and Chemistry of Materials
Faculty of sciences Ben msik, Casablanca
Morocco
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