[QE-users] About the k-points weights used for nscf calculation of pwscf.

[Hongyi Zhao]

Hi,

I'm learning the wannier90's example05 which includes a pwscf's nscf
calculation. The input file is located here:
https://github.com/wannier-developers/wannier90/blob/2f4aed6a35ab7e8b38dbe196aa4925ab3e9deb1b/examples/example05/diamond.nscf.

In the input file for this example, it uses the following k-points settings:

K_POINTS {crystal}
64
0.0000 0.0000 0.0000 0.0156250
0.0000 0.2500 0.0000 0.0156250
0.0000 0.5000 0.0000 0.0156250
0.0000 0.7500 0.0000 0.0156250
0.2500 0.0000 0.0000 0.0156250
0.2500 0.2500 0.0000 0.0156250
0.2500 0.5000 0.0000 0.0156250
0.2500 0.7500 0.0000 0.0156250
0.5000 0.0000 0.0000 0.0156250
0.5000 0.2500 0.0000 0.0156250
0.5000 0.5000 0.0000 0.0156250
0.5000 0.7500 0.0000 0.0156250
0.7500 0.0000 0.0000 0.0156250
0.7500 0.2500 0.0000 0.0156250
0.7500 0.5000 0.0000 0.0156250
0.7500 0.7500 0.0000 0.0156250
0.0000 0.0000 0.2500 0.0156250
0.0000 0.2500 0.2500 0.0156250
0.0000 0.5000 0.2500 0.0156250
0.0000 0.7500 0.2500 0.0156250
0.2500 0.0000 0.2500 0.0156250
0.2500 0.2500 0.2500 0.0156250
0.2500 0.5000 0.2500 0.0156250
0.2500 0.7500 0.2500 0.0156250
0.5000 0.0000 0.2500 0.0156250
0.5000 0.2500 0.2500 0.0156250
0.5000 0.5000 0.2500 0.0156250
0.5000 0.7500 0.2500 0.0156250
0.7500 0.0000 0.2500 0.0156250
0.7500 0.2500 0.2500 0.0156250
0.7500 0.5000 0.2500 0.0156250
0.7500 0.7500 0.2500 0.0156250
0.0000 0.0000 0.5000 0.0156250
0.0000 0.2500 0.5000 0.0156250
0.0000 0.5000 0.5000 0.0156250
0.0000 0.7500 0.5000 0.0156250
0.2500 0.0000 0.5000 0.0156250
0.2500 0.2500 0.5000 0.0156250
0.2500 0.5000 0.5000 0.0156250
0.2500 0.7500 0.5000 0.0156250
0.5000 0.0000 0.5000 0.0156250
0.5000 0.2500 0.5000 0.0156250
0.5000 0.5000 0.5000 0.0156250
0.5000 0.7500 0.5000 0.0156250
0.7500 0.0000 0.5000 0.0156250
0.7500 0.2500 0.5000 0.0156250
0.7500 0.5000 0.5000 0.0156250
0.7500 0.7500 0.5000 0.0156250
0.0000 0.0000 0.7500 0.0156250
0.0000 0.2500 0.7500 0.0156250
0.0000 0.5000 0.7500 0.0156250
0.0000 0.7500 0.7500 0.0156250
0.2500 0.0000 0.7500 0.0156250
0.2500 0.2500 0.7500 0.0156250
0.2500 0.5000 0.7500 0.0156250
0.2500 0.7500 0.7500 0.0156250
0.5000 0.0000 0.7500 0.0156250
0.5000 0.2500 0.7500 0.0156250
0.5000 0.5000 0.7500 0.0156250
0.5000 0.7500 0.7500 0.0156250
0.7500 0.0000 0.7500 0.0156250
0.7500 0.2500 0.7500 0.0156250
0.7500 0.5000 0.7500 0.0156250
0.7500 0.7500 0.7500 0.0156250

As you can see, it uses 0.0156250 as the weight of all k-points. I
can't figure out how to obtain this value.

OTOH, based on the notes here:
https://www.quantum-espresso.org/Doc/INPUT_PW.html#idm1126, It gives
the following instructions:


In a non-scf calculation, weights do not affect the results.
If you just need eigenvalues and eigenvectors (for instance,
for a band-structure plot), weights can be set to any value
(for instance all equal to 1).


It said that for a non-scf calculation, weights do not affect the
results. If so, why they still set weights for the k-points in the
example I mentioned above?

Any hints will be highly appreciated.
-- 
Hongyi Zhao <hongyi.zhao at gmail.com>