[QE-users] Alpha_mix not resolving ph.x convergence failure

[Jessica Johnson]

Hello QE users,

I am having trouble converging a phonons calculation. The archives indicate that many users were able to solve this problem reducing the default value of alpha_mix(1) to .1 or .2. I have tried many values from .01 - .9 and I end up with the calculation being unable to converge. In addition, I have lowered the convergence threshold for the scf calculation thinking that would set up the phonons calculation to converge more easily. I have also varied the nq1, nq2, k1 and k2 values. Neither of the latter two changes made much difference

I am using espresso + d3q (version number I am unsure of, however the release date is Dec. 12, 2021).

My ultimate goal is to use the d3_q2r.x and d3_qha.x executables to compute adsorption of H onto MoS2 layers.

Here are my pw.x and ph.x input files for H adsorbed onto the Mo site:
________________________________________________________

&CONTROL
   calculation     =  'scf'
   prefix          =  '1T_H_Mo_0'
   pseudo_dir      =  '.'
   title           =  '1T layers'
   verbosity       =  'high'
 /

 &SYSTEM
   A               =  6.385866
   B               =  6.385866
   C               =  14
   cosAB           =  -0.5
   cosAC           =  0
   cosBC           =  0
   degauss         =  0.005
   ecutrho         =  368
   ecutwfc         =  92
   ibrav           =  4
   input_dft       =  'BEEF-vdW'
   nat             =  13
   ntyp            =  3
   occupations     =  'smearing'
   smearing        =  'gaussian'
 /

 &ELECTRONS
   conv_thr        =  1e-10
 /

 &IONS
 /

 &CELL
   cell_dofree     =  'epitaxial_ab'
 /

ATOMIC_SPECIES
  Mo    95.95   Mo_HER.upf
  S    32.066   S_HER.upf
  H    1.00794   H_HER.upf


ATOMIC_POSITIONS crystal
Mo            0.0000010000       -0.0000010000        0.2432527978
S             0.3387936710        0.1693960855        0.1415931532
S             0.1716523937        0.3433032874        0.3652990281
H            -0.0000005000        0.0000000000        0.3685376338
Mo            0.4770138961       -0.0459752078        0.2481206178
S             0.8306049145        0.1693960855        0.1415931532
S             0.6666670000        0.3333325000        0.3420643699
Mo            0.4770138961        0.5229861039        0.2481206178
S             0.8306049145        0.6612073290        0.1415931532
S             0.6566962126        0.8283471063        0.3652990281
Mo            0.0459752078        0.5229861039        0.2481206178
S             0.3333345000        0.6666665000        0.1232508011
S             0.1716523937        0.8283471063        0.3652990281

K_POINTS automatic
  4   4   1   0   0   0

_____________________________________________________________


Phonon calculation 1T_H_Mo_0

&inputph
  prefix        = '1T_H_Mo_0'
  fildyn        = '1T_H_Mo_0.1.G'
  tr2_ph        = 1.0d-14
  alpha_mix(1)  = .1
  ldisp         = .true.
  nq1           = 4
  nq2           = 4
  nq3           = 1
/

___________________________________________________________

Thank you in advance for your help on this matter, as it is one of the tougher ones I have encountered using QE.

Jessica Johnson
graduate student
Materials Science and Engineering Department
Rutgers University, New Brunswick, New Jersey
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