# [Pw_forum] How to set variables when get symmetry operation # N not allowed?

Paolo Giannozzi p.giannozzi at gmail.com
Thu Feb 8 19:57:45 CET 2018

```There are no symmetries with fractional translations. Problem solved.

Paolo

On Thu, Feb 8, 2018 at 5:30 PM, Arena Konta <qe6user at gmail.com> wrote:

> Dear prof. Paolo Giannozzi
>
> Thank you for quick response. Please, clarify me: I set variable
> "use_all_frac=.true." and option "verbosity='high'" and get output showed
> below. Hoverwer, I am still unable to find the right values of frac. trans
> (n=1?) I have to calculate phonons,
> so i need to set right k-mesh.
>
>      8 Sym. Ops., with inversion, found
>
>
>                                     s                        frac. trans.
>
>       isym =  1     identity
>
>  cryst.   s( 1) = (     1          0          0      )
>                   (     0          1          0      )
>                   (     0          0          1      )
>
>  cart.    s( 1) = (  1.0000000  0.0000000  0.0000000 )
>                   (  0.0000000  1.0000000  0.0000000 )
>                   (  0.0000000  0.0000000  1.0000000 )
>
>
>       isym =  2     180 deg rotation - cart. axis [0,0,1]
>
>  cryst.   s( 2) = (    -1          0          0      )
>                   (     0         -1          0      )
>                   (    -1         -1          1      )
>
>  cart.    s( 2) = ( -1.0000000  0.0000000  0.0000000 )
>                   (  0.0000000 -1.0000000  0.0000000 )
>                   (  0.0000000  0.0000000  1.0000000 )
>
>
>       isym =  3      90 deg rotation - cart. axis [0,0,-1]
>
>  cryst.   s( 3) = (     0         -1          0      )
>                   (     1          0          0      )
>                   (     0         -1          1      )
>
>  cart.    s( 3) = (  0.0000000  1.0000000  0.0000000 )
>                   ( -1.0000000  0.0000000  0.0000000 )
>                   (  0.0000000  0.0000000  1.0000000 )
>
>
>       isym =  4      90 deg rotation - cart. axis [0,0,1]
>
>  cryst.   s( 4) = (     0          1          0      )
>                   (    -1          0          0      )
>                   (    -1          0          1      )
>
>  cart.    s( 4) = (  0.0000000 -1.0000000  0.0000000 )
>                   (  1.0000000  0.0000000  0.0000000 )
>                   (  0.0000000  0.0000000  1.0000000 )
>
>
>       isym =  5     inversion
>
>  cryst.   s( 5) = (    -1          0          0      )
>                   (     0         -1          0      )
>                   (     0          0         -1      )
>
>  cart.    s( 5) = ( -1.0000000  0.0000000  0.0000000 )
>                   (  0.0000000 -1.0000000  0.0000000 )
>                   (  0.0000000  0.0000000 -1.0000000 )
>
>
>       isym =  6     inv. 180 deg rotation - cart. axis [0,0,1]
>
>  cryst.   s( 6) = (     1          0          0      )
>                   (     0          1          0      )
>                   (     1          1         -1      )
>
>  cart.    s( 6) = (  1.0000000  0.0000000  0.0000000 )
>                   (  0.0000000  1.0000000  0.0000000 )
>                   (  0.0000000  0.0000000 -1.0000000 )
>
>
>       isym =  7     inv.  90 deg rotation - cart. axis [0,0,-1]
>
>  cryst.   s( 7) = (     0          1          0      )
>                   (    -1          0          0      )
>                   (     0          1         -1      )
>
>  cart.    s( 7) = (  0.0000000 -1.0000000  0.0000000 )
>                   (  1.0000000  0.0000000  0.0000000 )
>                   (  0.0000000  0.0000000 -1.0000000 )
>
>
>       isym =  8     inv.  90 deg rotation - cart. axis [0,0,1]
>
>  cryst.   s( 8) = (     0         -1          0      )
>                   (     1          0          0      )
>                   (     1          0         -1      )
>
>  cart.    s( 8) = (  0.0000000  1.0000000  0.0000000 )
>                   ( -1.0000000  0.0000000  0.0000000 )
>                   (  0.0000000  0.0000000 -1.0000000 )
>
>
> Thank you in avdance.
> Arena Konta
>
>
> ************************************************************
> *****************
>
> Set variable "use_all_frac=.true." and option "verbosity='high'". This will
> find and print all symmetries and associated fractional translations. If a
> fractional translation along a crystal axis is 1/n, with n integer, the FFT
> dimension along that axis must contain a factor n. If you do not need
> hybrid functionals or phonons, just set variable "use_all_frac=.true."
>
> Paolo
>
>
>
>
>
> 2018-02-07 20:18 GMT+01:00 Arena Konta <qe6user at gmail.com>:
>
>> Hi All,
>>
>> I read Troubleshooting and found out that "you can force your FFT grid to be commensurate with fractional translation (set variables nr1, nr2, nr3 to suitable values)". How to do this for the crystal structure presented below? I have tried to this for various k-mesh, but every time I get 6 symmetry operations are not compatible with FFT grid:
>>  warning: symmetry operation # 2 not compatible with FFT grid.
>>   -1 0 0
>>    0 -1 0
>>   -1 -1 1
>>      warning: symmetry operation # 3 not compatible with FFT grid.
>>    0 -1 0
>>    1 0 0
>>    0 -1 1
>>      warning: symmetry operation # 4 not compatible with FFT grid.
>>    0 1 0
>>   -1 0 0
>>   -1 0 1
>>      warning: symmetry operation # 6 not compatible with FFT grid.
>>    1 0 0
>>    0 1 0
>>    1 1 -1
>>      warning: symmetry operation # 7 not compatible with FFT grid.
>>    0 1 0
>>   -1 0 0
>>    0 1 -1
>>      warning: symmetry operation # 8 not compatible with FFT grid.
>>    0 -1 0
>>    1 0 0
>>    1 0 -1
>>
>> &SYSTEM
>>   ibrav = 0
>>   celldm(1) = 18.61847
>>   nat = 9
>>   ntyp = 2
>> /
>> CELL_PARAMETERS {alat}
>>   1.000000000000000 0.000000000000000 0.000000000000000
>>   0.000000000000000 1.000000000000000 0.000000000000000
>>   0.500000000000000 0.500000000000000 0.175193124160743
>>
>> ATOMIC_POSITIONS {crystal}
>> A 0.304370000000000 0.373120000000000 0.000000000000000
>> A 0.626880000000000 0.304370000000000 0.000000000000000
>> A 0.695630000000000 0.626880000000000 0.000000000000000
>> A 0.373120000000000 0.695630000000000 0.000000000000000
>> A 0.000000000000000 0.000000000000000 0.000000000000000
>> B 0.055910000000000 0.282920000000000 0.000000000000000
>> B 0.717080000000000 0.055910000000000 0.000000000000000
>> B 0.944090000000000 0.717080000000000 0.000000000000000
>> B 0.282920000000000 0.944090000000000 0.000000000000000
>>
>> K_POINTS automatic
>> 10 10 18 0 0 0
>>
>>
>>
>> --
>> with regards
>>
>> Arena Konta
>> The Institute of Thermophysics in Novosibirsk Scientific Center
>>
>>
>
>
> --
> with regards
>
> Arena Konta
> The Institute of Thermophysics in Novosibirsk Scientific Center
>
>
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--
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222
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