[Pw_forum] phonon calculation stops at a particular mode

[lung Fermin]

Dear QE community,

Recently, I am trying to calculate the phonon dispersion in LiOsO3 (with
R-3c space group). The program always stop at a mode which the scf cycle
does not converge after 100 iteration. I have tried reducing alpha_mix and
increasing the q-point density but the problem persists. The following are
the inputs and output. Any help or suggestions would be much appreciated.

::::::::::::::
scf.in <http://lioso3.scf.in/>
::::::::::::::
 &control
    calculation='scf',
    restart_mode='from_scratch',
    prefix='LiOsO3',
    outdir = './tmp/',
    pseudo_dir = '/pslibrary.1.0.0/pbe/PSEUDOPOTENTIALS/',
    max_seconds = 172000
 /
 &system
    nat = 10
    ntyp = 3
    ibrav = 5
    celldm(1) = 10.0031
    celldm(4) = 0.530117
    ecutwfc =60
    ecutrho=480
 /
 &electrons
!   mixing_beta=0.3D0,
!   mixing_ndim=10
    conv_thr=1.D-10
 /
 &ions
 /
&cell
 /
ATOMIC_SPECIES
Li  6.941  Li.pbe-sl-rrkjus_psl.1.0.0.UPF
Os  190.23  Os.pbe-spn-rrkjus_psl.1.0.0.UPF
O  15.999  O.pbe-n-rrkjus_psl.1.0.0.UPF
ATOMIC_POSITIONS crystal
Li       0.250000000   0.250000000   0.250000000
Li       0.750000000   0.750000000   0.750000000
Os       0.000000000   0.000000000   0.000000000
Os       0.500000000   0.500000000   0.500000000
O        0.623133124   0.876866876   0.250000000
O        0.376866876   0.123133124   0.750000000
O        0.876866876   0.250000000   0.623133124
O        0.123133124   0.750000000   0.376866876
O        0.250000000   0.623133124   0.876866876
O        0.750000000   0.376866876   0.123133124
K_POINTS AUTOMATIC
15 15 15 1 1 1

::::::::::::::
phGrid.in <http://lioso3.phgrid.in/>
::::::::::::::
 &inputph
   prefix='LiOsO3',
   outdir='./tmp/'
   ldisp=.true.
   fildyn='LiOsO3.dyn',
   nq1=4,
   nq2=4,
   nq3=4,
   alpha_mix(1)=0.05,
   tr2_ph=1.0d-10,
 /
::::::::::::::
(Some lines in the output)

      iter #  96 total cpu time : 75159.6 secs   av.it.:  38.6
      thresh= 1.755E-06 alpha_mix =  0.050 |ddv_scf|^2 =  2.806E-10

      iter #  97 total cpu time : 75686.1 secs   av.it.:  40.8
      thresh= 1.675E-06 alpha_mix =  0.050 |ddv_scf|^2 =  1.889E-10

      iter #  98 total cpu time : 76134.3 secs   av.it.:  33.7
      thresh= 1.374E-06 alpha_mix =  0.050 |ddv_scf|^2 =  1.803E-10

      iter #  99 total cpu time : 76695.2 secs   av.it.:  41.8
      thresh= 1.343E-06 alpha_mix =  0.050 |ddv_scf|^2 =  2.824E-10

      iter # 100 total cpu time : 77231.0 secs   av.it.:  41.2
      thresh= 1.680E-06 alpha_mix =  0.050 |ddv_scf|^2 =  3.136E-10

     End of self-consistent calculation

     No convergence has been achieved
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