[Pw_forum] q-mesh breaks symmetry

[Ari P Seitsonen]

Dear BENYAHIA NEZHA,

   Did you try without shifting the k points, so without k1 = k2 = k3? If I 
have understood correctly shifting the k points laterally away from the 
Gamma point in a hexagonal cell is not recommendable as the results grid 
of k points has a lower symmetry than the hexagonal one (for more details 
one can read my ancient PhD thesis, in particular the Appendices ;).

     Greetings,

        apsi

PS You have a very creative way of creating home directories, or even 
users - one for each job? ;)

-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-
   Ari Paavo Seitsonen / Ari.P.Seitsonen at iki.fi / http://www.iki.fi/~apsi/
   Institut für Chemie der Universität Zürich, CH-8057 Zürich
   Tel: +41 44 63 54 497  /  Mobile: +41 79 71 90 935


On Mon, 21 Apr 2014, BENYAHIA NEZHA wrote:

> I'd like to calculate phonon frequencies of compound InAs on the Wurtzite structure, using the input files that i pasted below, the Scf
> calculation was done normally, however phonons calculation crashes and display me this error message on the output file.
>  
> 
>      This q-mesh breaks symmetry!
>      Try to choose different nq1, nq2, nq3
>      You can also continue by setting search_sym=.false.
>      but be careful because q2r will not work
> 
>  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>      Error in routine q_points (1):
>      q-mesh breaks symmetry
>  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> 
> When i took (nq1, nq2, nq3)=(4 4 4) it worked, but according to my knowledge when we are on the wurtzite structure nq1=nq2≠nq3. I'd like
> also to understand how to choose (nq1, nq2, nq3). I really appreciate if anyone can help me to find out the problems.
> 
> input files:
>  &control
>     calculation='scf'
>     restart_mode='from_scratch',
>     tstress = .true.
>     tprnfor = .true.
>     prefix='InAs2h',
>     pseudo_dir = '/home/InAs.lda/Pseudo',
>     outdir='/home/InAs.lda/Temp'
>  /
>  &system
>     ibrav=  4, celldm(1) =8.00,celldm(3) =1.633, nat= 4, ntyp= 2,
>     ecutwfc =60.0,
>  /
>  &electrons
>     diagonalization='david'
>     conv_thr =1.0e-7
>     mixing_beta = 0.7
>  /
> ATOMIC_SPECIES
>  In   114.818 In.PZ.UPF
>  As   74.9216 As.PZ.UPF
> ATOMIC_POSITIONS crystal
> In  0.00000000 0.00000000 0.00000000
> In  0.33333333 0.66666667 0.50000000
> As  0.00000000 0.00000000 0.37500000
> As  0.33333333 0.66666667 0.87500000
> 
> K_POINTS (automatic)
>  4 4 3 1 1 1
> 
> phonons of InAs
>  &inputph
>   tr2_ph=1.0d-14,
>   prefix='InAs',
>   ldisp=.true.,
>   nq1=4, nq2=4, nq3=3
>   amass(1)=114.818,
>   amass(2)=74.9216,
>     outdir='/home/InAs.lda/Temp/',
>   fildyn='InAs.dyn',
>  /
> 
> 
>