# [Pw_forum] PWscf can not find out symmetry operations!!!

Stefano Baroni baroni at sissa.it
Thu Aug 31 04:01:40 CEST 2006

```On Aug 31, 2006, at 3:28 AM, Ó¢Àû Å£ wrote:

> Dear Pro. Baroni
> Thanks a lot for your help!
>   I have said that It was no use to set accep=1.0D-2
> and recompiled pw.x. The program still could not find
> any symmetry operation.
>   Then I selected 7 inequivalent atoms, then used 8
> symmetry operations:
>   x,y,z
>   -x,-y,z
>   -x+1/2,y+1/2,-z
>   x+1/2,-y+1/2,-z
>   -x+1/2,-y+1/2,-z
>   x+1/2,y+1/2,-z
>   x,-y,z
>   -x,y,z
> to transform the 7 inequivalent atoms to 20 atoms in
> the primary unit cell.

I can hardly understand what you did. If by applying some symmetry
operations to a bunch of positions ("atoms") you obtain a larger
number of atoms, doesn't this mean that those operations are not
"symmetrry operations"???

>   Then I ran scf. I use Norm-Conserving PP and chose
> ecutwfc=70,ecutrho=600.

there is ABSOLUTELY no point in using ecutrho>ecutwfc with norm
conserving PP's

>   There appeared message "warning:symmetry operation #
>  3/4/5/6 not allowed  fractional translation:" in the
> out file as discussed before. Only 4 symmetry
> operations without inversion could be found!
> I set ecutrho = 500 and calculated it again. Then
> all 8 symmetry operations was found!
>   The stress tensor did not change too much!
>   stress tensor(kbar) from original atom positions:
>     49.20      0.01      0.07
>      0.01    -16.72      0.16
>      0.07      0.16      2.61
>   stress tensor(kbar) from changed atom positions:
>     49.98      0.00      0.00
>      0.00    -16.13      0.00
>      0.00      0.00      7.30
>   All the nondiagonal elements changed to 0.00.
>   I think changed accpe from 1.0D-5 to 1.0D-2 will be
> harmful for the calculations. So I reset it to 1.0D-5
> and recompiled.
>   I have no other method to make the program find out
> all 8 symmetry operations than this method.

Have you browsed in the mailing list's archive, as I suggested?
Please, let me NOT rediscuss this point that I and others discussed
the last time a few days ago

>
>   Another question:
>   I use Yahoo mail box. How can I post the reply
> message next to the message which is replied in the
> mailing list. I alway started a new discussion line
> with reply message! Sorry for that!

SB

---
Stefano Baroni - SISSA  &  DEMOCRITOS National Simulation Center -
Trieste
[+39] 040 3787 406 (tel) -528 (fax) / stefanobaroni (skype)

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