[Wannier] Reciprocal vectors in wannier90 vs Quantum espresso

[Nicola Marzari]

Dear Youssef,

the vectors seems to me to be the same - Wannier 90  writes those in units
of 1/Angstrom, while QE writes them in units of 2 pi/alat, where alat is
celldm(1), and it is in Bohr. So e.g. the z component of
b2 is 0.457131 1/Ang in Wannier90, and is 0.407234 in QE. Now,

0.407234 * 2 * pi / 10.577485 gives 0.2419031 1/Bohr, that is
exactly 0.457131 1/Ang (1 Bohr = 0.529177 Ang)

			nicola


On 03/12/2016 21:54, Youssef Aharbil wrote:
> 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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> Wannier mailing list
> Wannier at quantum-espresso.org
> http://mailman.qe-forge.org/cgi-bin/mailman/listinfo/wannier
>

-- 
----------------------------------------------------------------------
Prof Nicola Marzari, Chair of Theory and Simulation of Materials, EPFL
Director, National Centre for Competence in Research NCCR MARVEL, EPFL
http://theossrv1.epfl.ch/Main/Contact http://nccr-marvel.ch/en/project