[QE-users] how to deal with the abnormal phonon spectrum oscillation

[zhouchao]

Hello, everyone,I have encountered some problems with my phonon spectrum calculation, and I have consulted many people without getting a good solution.
my scf input mainly was written as 
 &system
        ibrav= 0,
        nat= 6
        ntyp= 3
        ecutwfc=80
        ecutrho=800
        occupations='smearing',
        smearing='mp',
        degauss=0.03,
        la2F = .true.,
 /
 &electrons
   conv_thr = 1.0d-8
   mixing_beta = 0.4,
   electron_maxstep = 999,

ATOMIC_SPECIES
Mo   95.9   Mo.UPF
Ti   47.9   Ti.UPF
B   10.8   B.UPF
CELL_PARAMETERS (angstrom)
    3.04653557  0.00000000  -0.00000000
    -1.52326778  2.63837719  -0.00000000
    0.00000000  0.00000000  6.42968751
ATOMIC_POSITIONS (crystal)
Mo 0.000000000 -0.000000000 0.000000000
Ti 0.000000000 -0.000000000 0.500000000
B 0.333333343 0.666666687 0.255684047
B 0.666666627 0.333333313 0.744315953
B 0.666666627 0.333333313 0.255684047
B 0.333333343 0.666666687 0.744315953
K_POINTS {automatic}
20 20 12 0 0 0



and my phonon calculation was written as
Electron-phonon coefficients for LuH13
 &inputph
  tr2_ph=1.0d-14
  prefix='Mo1Ti1B4',
  fildvscf='Mo1Ti1B4dv',
  amass(1)=95.9
  amass(2)=47.9
  amass(3)=10.8
  alpha_mix=0.3
  outdir='./tmp',
  fildyn='Mo1Ti1B4.dyn',
  electron_phonon='interpolated',
  el_ph_sigma=0.005,
  el_ph_nsigma=10,
  trans=.true.,
  ldisp=.true.,
  start_q=10
  last_q=10
  nq1 = 5,nq2 = 5,nq3 = 3
 /
 The output phonon spectrum was drawn as 

 
There are some abnormal oscillations in its phonon spectrum. I tried changing the pseudopotential and qe versions, and also tried different smearing, and some of them even failed to converge. So how to deal with this problem, if it is a problem with the structure of the system itself, how should we explain such a problem? Thank you for your help.


zhouchao
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