# [Pw_forum] Error in routine punch_band_2d (1): Problems with k points

Youssef Aharbil aharbil at gmail.com
Tue Jan 19 14:42:26 CET 2016

```Dear all,

I am studying a double perovskite band structure under a trigonal crystal
system (ibrav = 5), the Brillouin zone sampling has been performed using
this path:

K_POINTS tpiba_b
11
gG 25
L  25
B1 1
B  25
Z  25
gG 25
X  1
Q 25
F 25
P1 25
Z  1
L  25
P 1

all calculations run well, till the stage of the extraction of bands using
bands.x, I got this error while plot_2D = .true.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Error in routine punch_band_2d (1):
Problems with k points
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

stopping ...

The problem disappear when plot_2D = .false..

This error has been already posted in a previous thread, Prof Paolo
suggested to check these conditions (from bands.f90) :

!  This routine opens a file for each band and writes on output
!  kx, ky, energy,
!  kx, ky, energy
!  .., .., ..
!  where kx and ky are proportional to the length
!  of the vectors k_1 and k_2 specified in the input of the 2d plot.
!
!  The k points are supposed to be in the form
!  xk(i,j) = xk_0 + dkx *(i-1) + dky * (j-1)      1<i<n1, 1<j<n2
!
!  kx(i,j) = (i-1) |dkx|
!  ky(i,j) = (j-1) |dky|

I can't check since i don't understand well what they are.

Any thoughts or hints are welcomed.

Youssef Aharbil,

Laboratory of Physics and Chemistry of Materials

Faculty of sciences Ben msik, Casablanca

Morocco
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