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

[Pietro Davide Delugas]

Hello
many times it works better if you reduce alpha_mix gradually. For 
example with

alpha_mix(10) = 0.3

and

alpha_mix (15) = 0.1

you use default value for alpha_mix in first 10 iterations, then  you 
reduce it to 0.3, and to 0.1 after 15th iteration.

Pietro

On 5/13/22 00:06, Jessica Johnson wrote:
> 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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