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

[Ó¢Àû Å£]

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

  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!


On Aug 29, 2006, at 18:24:05 +0200, Stefano Baroni
wrote:
>Dear Niu Ying Li,
>
>this very same question has been discussed many
>times in this forum, 
>=20
>the last of which only a few days ago. Would you be
>so kind as to =20
>browse the archive of the mailing list and revert us
>after finding =20
>and reading the some of the relevant posts, in case
>the situation is 
>=20
>not yet clear to you?
>
>Many thanks for your interest in Quantum ESPRESSO
>
>Stefano Baroni
>
>On Aug 29, 2006, at 6:16 PM, =D3=A2=C0=FB =C5=A3
>wrote:
>
>> Dear all,
>>   I am calculate properties of diamond
>> surface(001),the lattice parameters of the slab
>>is :
>> 2.5221A,5.0442A,16.0253A,90,90,90
>> after atoms relax ,the atom positions(crystal) are:
>> C     0.24978  -0.11238   0.21129
>>
>> C     0.24980   0.60988   0.21129
>>
>> C     0.74978  -0.01422   0.17583
>>
>> C     0.74980   0.51175   0.17582
>>
>> C     0.74981   0.24879   0.13029
>>
>> C     0.74981   0.74881   0.11624
>>
>> C     0.24982   0.24883   0.07780
>>
>> C     0.24982   0.74885   0.07061
>>
>> C     0.24984  -0.00014   0.02461
>>
>> C     0.24984   0.49787   0.02461
>>
>> C     0.74985  -0.00211  -0.02461
>>
>> C     0.74986   0.49988  -0.02461
>>
>> C     0.74987   0.24889  -0.07061
>>
>> C     0.74987   0.74888  -0.07780
>>
>> C     0.24987   0.24889  -0.11624
>>
>> C     0.24988   0.74888  -0.13029
>>
>> C     0.24990   0.01186  -0.17582
>>
>> C     0.24987   0.48589  -0.17583
>>
>> C     0.74990   0.11000  -0.21129
>>
>> C     0.74987   0.38773  -0.21129
>>
>>
>> but PWscf can not find any symmetry operations of
>>the
>> system.
>> I setup the struct and use Material Studio find 8
>> space group operations include inversion! The
>> tolerance is 0.01A.
>>
>> Then I read PW manual:
>>
>> the number of significant figures in the atomic
>> positions is not large enough. In file
>>PW/eqvect.f90,
>> the variable accep is used to decide whether a
>> rotation is a symmetry operation. Its current value
>> (10-5 ) is quite strict: a rotated atom must
>>coincide
>> with another atom to 5 significant digits. You may
>> change the value of accep and recompile.
>>
>> I change accep from 1.0d-5 to 1.0d-2 then to 1.0d-1
>> ,but PWscf still find no symmetry.
>>
>> What should I do?
>> Why pwscf choose 1.0d-5,so strict?


__________________________________________________
Do You Yahoo!?
Tired of spam?  Yahoo! Mail has the best spam protection around 
http://mail.yahoo.com