[Wannier] ndegen variable in plot.F90

[Jonathan Yates]

On 10 Mar 2010, at 13:39, Gianluca Giovannetti wrote:
>
> Once i get the H(n,m,R) in the file _hr.dat (in which are printed   
> irvec(:,loop_rpt) and ham_r(:,:,loop_rpt)  as coded  in  
> hamiltonian.F90)  i usually work  postprocessing it and  i can get  
> the correct Fourier Trasform (i can check the bands structure for  
> example) only if i use ndegen as above (the values of this variable  
> can be printed out with "iprint =3").
>
> this variable ndegen is updated in hamiltonian.F90  at the  
> subroutine hamiltonian_wigner_seitz(count_pts)  but i have problem  
> to understand what it is.
> could you give me some more details?

  For H(n,m,R) the set of R (lattice vectors) are chosen to lie within  
a Wigner-Seitz supercell. Some of the points lie on the edge of this  
supercell (ie they are shared by ndegen cells) and so only count  
fractionally in the fourier transform.
  [there are other options here - look at bands_plot_mode=cut and the  
comments in the subroutine plot_cut_hr]

  This is discussed in section II.B.1 of Phys. Rev. B 75, 195121 (2007)

Note that the latest version of wannier90 (v1.2) ndegen is included in  
the file seedname_hr.dat.

  Jonathan





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