[Pw_forum] Doubt in ibrav = 7

Tone Kokalj tone.kokalj at ijs.si
Fri Sep 19 07:58:12 CEST 2014

On Sat, 2014-09-13 at 22:39 +0100, Youssef Aharbil wrote:
> Dear QE Users,
> I have encountered lot of problems with ibrav = 7, when plotting the
> structure with xcrysden it seems that the atoms aren't at the right
> positions, using "crystal" for ATOMIC_POSITIONS give incorrect atoms
> coordinates while visualization, 

Such problems typically stem from lattice definition mismatches, e.g,
the user and pw.x use two different cell-definitions.
E.g., see this thread:

> I corrected that issue using "bohr" in stead off "crystal"  (of course
> by doing conversion), but it seems that one atom is missing (Second La
> atom with coordinate 0.5 0 0.25 ) even if it exist well in the input
> file.
> Please tell me if that's just a bug on xcrysden or something is wrong with my data.

Your structure looks OK and there is no missing atom, although it may
appear otherwise. The reason is that due to some round-off error two
periodic replicas of the La atom are not drawn (but notice that they are
periodic replicas); sometimes this happens and it is inconvenient. If
you drawn more units cells (say, 2x2x1) you will notice that noting is
missing (i.e. these replicas will appear).

Best regards,
Anton Kokalj
J. Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia 
(tel: +386-1-477-3523 // fax:+386-1-477-3822)

Please, if possible, avoid sending me Word or PowerPoint attachments.
See:  http://www.gnu.org/philosophy/no-word-attachments.html

More information about the users mailing list