[QE-users] sternheimer_kernel: root not converged in phonon calculations

[pboulet]

Dear all,

I am encountering the problem mentioned in the subject of this post.

Do you know to solve this problem?

I am running ph.x on Mg2Si (not a big deal!) with NC pseudopotentials from dojo website.
I have optimized the structure, then ran a SCF with 60 k-points.

Here is the input for ph.x:
Mg2Si Phonon
&inputph
  verbosity   = 'high',
  alpha_mix(1)= 0.1,
  tr2_ph      = 1.0d-12,
  diagonalization = 'cg',
  prefix      = 'Mg2Si',
  ldisp       = .true.,
  epsil       = .true.,
  lqdir       = .true.,
  search_sym  = .false.
  fildyn      = 'Mg2Si.dyn.xml',
  fildvscf    = 'dvscf'
  recover     = .true.,
  start_q = 2, last_q = 8,
  nq1=4, nq2=4, nq3=4,
/

and a sample of the output:
iter #  41 total cpu time :  5901.1 secs   av.it.: 210.4
      thresh= 1.000E-02 alpha_mix =  0.100 |ddv_scf|^2 =  1.350+100
     kpoint   3 sternheimer_kernel: root not converged, thresh <  3.699E+06
     kpoint   4 sternheimer_kernel: root not converged, thresh <  2.570E+03
     kpoint   5 sternheimer_kernel: root not converged, thresh <  1.322E+43
     kpoint   6 sternheimer_kernel: root not converged, thresh <  4.836E+01
     kpoint   7 sternheimer_kernel: root not converged, thresh <  2.110E-01
     kpoint  12 sternheimer_kernel: root not converged, thresh <  2.237E+25
     kpoint  13 sternheimer_kernel: root not converged, thresh <  1.420E+01
     kpoint  14 sternheimer_kernel: root not converged, thresh <  1.199E+21
     kpoint  15 sternheimer_kernel: root not converged, thresh <  6.741E+07
     kpoint  18 sternheimer_kernel: root not converged, thresh <  8.917E+00

Note that the calculation ran fine for the Gamma point, so in the present run I ‘recovered’ for k-points 2 to 8. 

The input file for the SCF calculation is:
&CONTROL
  title          = 'Mg2Si',
  calculation    = 'scf',
  etot_conv_thr  = 1d-9,
  tprnfor        = .true.,
  tstress        = .true.,
  restart_mode   = 'restart',
  verbosity      = 'high',
  prefix         = 'Mg2Si',
  wf_collect     = .true.,
/
&SYSTEM
  ibrav          = 2,
  celldm(1)      = 12.037d0,
  nat            = 3,
  ntyp           = 2,
  ecutwfc        = 100.d0,
  ecutrho        = 400.d0,
  occupations    = 'fixed',
  nbnd           = 20,
/
&ELECTRONS
  conv_thr       = 1d-12,
  mixing_beta    = 0.2d0,
/
ATOMIC_SPECIES
Mg 24.3 Mg.upf
Si 28.1 Si.upf

ATOMIC_POSITIONS crystal
Si       0.000000000   0.000000000   0.000000000
Mg       0.250000000   0.250000000   0.250000000
Mg       0.750000000   0.750000000   0.750000000

K_POINTS automatic
8 8 8 1 1 1

Thank you for your help and time.
Best regards,
Pascal

.
Pascal Boulet
—
Professor in computational materials chemistry - DEPARTMENT OF CHEMISTRY
University of Aix-Marseille - Avenue Escadrille Normandie Niemen - F-13013 Marseille - FRANCE
Tél: +33(0)4 13 55 18 10 - Fax : +33(0)4 13 55 18 50
Email : pascal.boulet at univ-amu.fr <mailto:pascal.boulet at univ-amu.fr>




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