[Pw_forum] big differences in relativistic phonon calculations between v5.0 and v5.3

[Paolo Giannozzi]

On Sun, 2013-04-07 at 03:55 +0200, Alaska Subedi wrote:

> Things work again in the svn version

maybe it is related to this issue mentioned in the Doc/release-notes
file?
=====================
Fixed in svn version:
[...]
   * PHonon: the recently introduced symmetry Sq=-q+G has still some
     problem: currently disabled
=====================
It should have been fixed in v.5.0.3 as well, but maybe it wasn't.
If you have a different nunber of k-points in the "good" vs the "bad"
phonon calculation, this might be the reason

> Sorry for the noise

there was some signal as well

P.
> 
> Alaska
> 
> On Sun, Apr 7, 2013 at 2:45 AM, Alaska Subedi <asubedi at gmail.com> wrote:
> > Dear all,
> >
> > When I calculate the phonon dispersions of PbTe using the relativistic
> > pseudopotentials from pslibrary, I find that v5.0 gives stable phonon
> > dispersions while v5.3 (and v5.2 as well) gives unstable phonons along
> > q = (0, x, 0). There is also a published work
> > http://prb.aps.org/abstract/PRB/v85/i18/e184303 with stable PbTe
> > phonons using relativistic pseudopotentials of pslibrary. However, I
> > cannot get stable phonon frequencies anymore with the new version of
> > the code with the sets of relativistic pseudopotentials that I tried:
> > lda and gga ultrasoft and normconserving.
> >
> > Could anyone please check what has gone wrong in newer versions?
> >
> > The input files are below.
> >
> > PbTe.scf.in:
> >
> > &control
> >     calculation = 'scf'
> >     restart_mode = 'from_scratch',
> >     tprnfor = .true.
> >     tstress = .true.
> >     prefix = 'PT-ph2',
> >     pseudo_dir = './pseudo/'
> >     outdir = './tmp/'
> > /
> >
> > &system
> >     ibrav = 2
> >     celldm(1) = 12.056453 ! 6.38 angstroms
> >     nat = 2
> >     ntyp = 2
> >     ecutwfc = 50
> >     ecutrho = 500
> >     occupations = 'fixed'
> >     lspinorb = .true.
> >     noncolin = .true.
> > /
> >
> > &electrons
> >     conv_thr = 1.0d-12
> > !    diagonalization = 'cg'
> > !    mixing_mode = 'local-TF' ! 'plain'
> >     mixing_beta = 0.2d0
> > /
> >
> > ATOMIC_SPECIES
> >  Pb  207.21      Pb.rel-pz-dn-rrkjus_psl.0.2.2.UPF
> >  Te  127.60      Te.rel-pz-dn-rrkjus_psl.0.2.2.UPF
> > ATOMIC_POSITIONS crystal
> > Pb       0.500   0.500  0.500
> > Te       0.000   0.000  0.000
> > K_POINTS automatic
> >   8  8  8  0  0  0
> >
> >
> > PbTe.ph.in:
> >
> > &inputph
> >   tr2_ph=1.0d-18,
> >   prefix='PT-ph2',
> >   alpha_mix(1)=0.2,
> >   nmix_ph=5,
> >   amass(1) = 207.21
> >   amass(2) = 127.60
> >   outdir='./tmp/',
> >   fildyn='PT-ph0.dyn2'
> > /
> >    0.000000000000000E+00   0.5000000000000E+00   0.000000000000000E+00
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-- 
Paolo Giannozzi, Dept. Chemistry&Physics&Environment, 
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222