[Pw_forum] PWscf can not find out symmetry operations!!!
Ó¢Àû Å£
niuyingli at yahoo.com.cn
Thu Aug 31 03:28:17 CEST 2006
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?
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