[Pw_forum] Order of the q in the star for each dyn files

[Samuel Poncé]

Dear Lorenzo,

The q2qstar should give the same order but it does not.

Actually there is more than the order. The signs can be different.

For example I get
0.5 0.5 0.5 in the sxq variable of the phonon code and -0.5 -0.5 -0.5 in
the sxq variable of the q2qstar code.

I know that it is the same point in diamond but this can leads to problems,
especially when the crystal does not respect time reversal (maybe in that
case the code produce the same result, I did not test).
Additionally, it does not really make sense that they produce different
results.

My scf.in input is
 &control
    calculation     = 'scf'
    prefix          = 'diam'
    restart_mode    = 'from_scratch'
    wf_collect      = .false.
    pseudo_dir      = '../../pp'
    outdir          = './'
    tprnfor         = .true.
    tstress         = .true.
 /
 &system
    ibrav           = 2
    celldm(1)       = 6.64245
    nat             = 2
    ntyp            = 1
    ecutwfc         = 40
    nbnd            = 4
 /
 &electrons
    diagonalization = 'david'
    mixing_beta     = 0.7
    conv_thr        = 1.0d-10
 /
ATOMIC_SPECIES
  C  12.01078  C.UPF
ATOMIC_POSITIONS alat
  C   0.00  0.00  0.00
  C   0.25  0.25  0.25
K_POINTS automatic
4 4 4 1 1 1

My ph.in input is
  prefix   = 'diam',
  epsil    = .true.,
  fildyn   = 'diam.dyn',
  ldisp    = .true.
  fildvscf = 'dvscf'
  nq1=6,
  nq2=6,
  nq3=6,
  tr2_ph   =  1.0d-12,
 /

Best Regards,

Samuel Ponce,
Department of Materials, University of Oxford





2015-06-05 21:57 GMT+01:00 Lorenzo Paulatto <lorenzo.paulatto at impmc.upmc.fr>
:

>
>
> On 05/06/15 22:26, Samuel Poncé wrote:
> > Dear all,
> >
> > I'm a bit confused by the ordering of the q points that belong to the
> > star of a q-point.
>
> Dear Samuel,
> the order is not important, if for some reason you need a specific order
> your code is going to break sooner or later.
>
> Anyway, q2qstar uses the same subroutines as phonon, so in principle it
> should give the same order. If you have a valid reason for requiring the
> same order and if you provide enough input and example files to
> reproduce your case, I may have a look.
>
> regards
> > --
> > Dr. Lorenzo Paulatto
> > IdR @ IMPMC -- CNRS & Université Paris 6
> > +33 (0)1 44 275 084 / skype: paulatz
> > http://www-int.impmc.upmc.fr/~paulatto/
> > 23-24/4é16 Boîte courrier 115, 4 place Jussieu 75252 Paris Cédex 05
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