[QE-users] Problem with tetrahedra method: from tetra_init : error # 26, cannot remap grid on k-point list

[Pacome NGUIMEYA]

Dear Pietro,

I ran the scf calculation follows by the nscf calculation with
occupation='smearing', smearing and degauss (with QE-6.3.0). 
I added  bz_sum = 'tetrahedra_opt' in the dos.x input file and I ran 
it but, it crashed and I got the following error message

     task #         0
     from dos : error #        19
     reading dos namelist

Apparently, the tetrahedron method is used if

         - "the input data file has been produced by pw.x using the
option
            occupations='tetrahedra', AND"
         - "a value for degauss is not given as input to namelist &dos"

read here https://gitlab.com/QEF/q-e/blob/qe-6.3/PP/Doc/INPUT_DOS.txt

But pw.x (nscf) does not work in my case

Further research on the internet led me to this website 
https://eamonnmurray.gitlab.io/modelling_materials/lab04/ where I could
read that
 
"Essentially this corresponds to doing a three dimensional linear
interpolation from a regular grid of values."..."It’s important to note
that in a real measurement of the density of states of a system the
there is an implicit broadening that comes from

1. Electron-phonon coupling: the states are not simply at a fixed
energy, but will have some distribution as the atoms vibrate.

2. Any measurement probe will have a finite energy width associated
with it, which will limit how finely it can resolve density of states
features.

So while tetrahedron may seem the more accurate approach, you shouldn’t
necessarily think of it as a more correct representation of a real
system."

I think I am just going to use the common way, that is, running the
nscf calculation with smearing and degaus. Then, run this code

&DOS
		prefix = '...',
		outdir = '...',
		fildos = '....dos.dat',
 /
and plot the DOS.

Regards - Pacome