# [Pw_forum] K-Points and dipole correction

Daniele Passerone Daniele.Passerone at empa.ch
Tue Mar 13 13:04:48 CET 2007

```Dear collegues,

I have a strange problem with a slab calculation with the Bengtsson
dipole correction (sawlike potential). The cell is hexagonal.

If I submit two different jobs, jobA and jobB (espresso 3.2.1 on IBM
power5 , but the same problem appears on a linux cluster) with
from_scratch scf optimization,

*) jobA:

in &control:
tefield=.false.,
dipfield=.false.
and:
K_POINTS {automatic}
5 5 1 1 1 0

*) jobB:

in &control:
tefield=.true.,
dipfield=.true.

in &system:
edir=3,
eamp=0.,
emaxpos=0.45
eopreg=0.05,

In the first case, I get 39 K points,
in the second case I get 13 K points. There is no symmetry found in the
slab in both cases.
Only 10 k points are common to both cases (marked by a star, see
below).

Why?

Probably I am missing something really fundamental here, and I would be
grateful for any help.
Daniele Passerone

jobA:
*      k(    1) = (   0.1000000   0.1732051   0.0000000), wk =
0.0533333
*     k(    2) = (   0.1000000   0.4041452   0.0000000), wk =
0.0533333
*     k(    3) = (   0.1000000  -0.5196152   0.0000000), wk =
0.0533333
*     k(    4) = (   0.1000000  -0.2886751   0.0000000), wk =
0.0533333
*     k(    5) = (   0.1000000  -0.0577350   0.0000000), wk =
0.0533333
*     k(    6) = (   0.3000000   0.5196152   0.0000000), wk =
0.0533333
*     k(    7) = (   0.3000000  -0.4041452   0.0000000), wk =
0.0533333
*     k(    8) = (   0.3000000  -0.1732051   0.0000000), wk =
0.0533333
*     k(    9) = (  -0.5000000  -0.8660254   0.0000000), wk =
0.0266667
k(   10) = (  -0.1000000   0.1732051   0.0000000), wk =
0.0533333
k(   11) = (   0.2000000   0.0000000   0.0000000), wk =
0.0533333
k(   12) = (  -0.1000000   0.4041452   0.0000000), wk =
0.0533333
k(   13) = (  -0.3000000   0.2886751   0.0000000), wk =
0.0533333
k(   14) = (   0.4000000   0.1154701   0.0000000), wk =
0.0533333
k(   15) = (  -0.3000000  -0.2886751   0.0000000), wk =
0.0533333
k(   16) = (   0.4000000  -0.1154701   0.0000000), wk =
0.0533333
k(   17) = (  -0.1000000  -0.5196152   0.0000000), wk =
0.0533333
k(   18) = (   0.5000000  -0.1732051   0.0000000), wk =
0.0533333
k(   19) = (  -0.4000000  -0.3464102   0.0000000), wk =
0.0533333
k(   20) = (   0.5000000   0.1732051   0.0000000), wk =
0.0533333
k(   21) = (  -0.4000000   0.3464102   0.0000000), wk =
0.0533333
k(   22) = (  -0.1000000  -0.2886751   0.0000000), wk =
0.0533333
k(   23) = (   0.3000000  -0.0577350   0.0000000), wk =
0.0533333
k(   24) = (  -0.2000000  -0.2309401   0.0000000), wk =
0.0533333
*     k(   25) = (   0.3000000   0.0577350   0.0000000), wk =
0.0533333
k(   26) = (  -0.2000000   0.2309401   0.0000000), wk =
0.0533333
k(   27) = (  -0.1000000  -0.0577350   0.0000000), wk =
0.0533333
k(   28) = (   0.0000000  -0.1154701   0.0000000), wk =
0.0533333
k(   29) = (  -0.3000000   0.5196152   0.0000000), wk =
0.0533333
k(   30) = (   0.6000000   0.0000000   0.0000000), wk =
0.0533333
k(   31) = (  -0.3000000  -0.4041452   0.0000000), wk =
0.0533333
k(   32) = (   0.5000000   0.0577350   0.0000000), wk =
0.0533333
k(   33) = (  -0.2000000  -0.4618802   0.0000000), wk =
0.0533333
k(   34) = (   0.5000000  -0.0577350   0.0000000), wk =
0.0533333
k(   35) = (  -0.2000000   0.4618802   0.0000000), wk =
0.0533333
k(   36) = (  -0.3000000  -0.1732051   0.0000000), wk =
0.0533333
k(   37) = (   0.0000000  -0.3464102   0.0000000), wk =
0.0533333
k(   38) = (   0.5000000  -0.8660254   0.0000000), wk =
0.0266667
k(   39) = (  -1.0000000   0.0000000   0.0000000), wk =
0.0266667

jobB:
k(    1) = (   0.1000000   0.1732051   0.0000000), wk =
0.1600000
k(    2) = (   0.1000000   0.4041452   0.0000000), wk =
0.1600000
k(    3) = (   0.1000000  -0.5196152   0.0000000), wk =
0.1600000
k(    4) = (   0.1000000  -0.2886751   0.0000000), wk =
0.1600000
k(    5) = (   0.1000000  -0.0577350   0.0000000), wk =
0.1600000
k(    6) = (   0.3000000   0.2886751   0.0000000), wk =
0.1600000
k(    7) = (   0.3000000   0.5196152   0.0000000), wk =
0.1600000
k(    8) = (   0.3000000  -0.4041452   0.0000000), wk =
0.1600000
k(    9) = (   0.3000000  -0.1732051   0.0000000), wk =
0.1600000
k(   10) = (   0.3000000   0.0577350   0.0000000), wk =
0.1600000
k(   11) = (  -0.5000000  -0.1732051   0.0000000), wk =
0.1600000
k(   12) = (  -0.5000000   0.0577350   0.0000000), wk =
0.1600000
k(   13) = (  -0.5000000  -0.8660254   0.0000000), wk =
0.0800000

~

```