[QE-users] Phonon SCF does not converge with semicore pseudopotentials

[Antonio Crepaldi]

Dear QE developers and users,

I'm currently trying to compute the phonon dispersion of a MoTe2 bilayer
with QE 6.8. I'm using the stringent accuracy, FR pseudopotentials from
PseudoDojo, which contain semicore states for Te as well.
I'm using vdW-DFT as vdw-df2-b86r.
I've carefully optimized the cell and the atomic position, however the scf
in the phonon calculation does not converge. In fact, it seems to diverge
straight away:

 Electric Fields Calculation
>       iter #   1 total cpu time :   118.9 secs   av.it.:  10.2
>       thresh= 1.000E-02 alpha_mix =  0.400 |ddv_scf|^2 =  4.707E-01
>       iter #   2 total cpu time :   150.1 secs   av.it.:   9.8
>       thresh= 1.000E-02 alpha_mix =  0.400 |ddv_scf|^2 =  1.742E+01
>       iter #   3 total cpu time :   170.5 secs   av.it.:   4.8
>       thresh= 1.000E-02 alpha_mix =  0.400 |ddv_scf|^2 =  1.238E+01
>       iter #   4 total cpu time :   190.2 secs   av.it.:   4.5
>       thresh= 1.000E-02 alpha_mix =  0.400 |ddv_scf|^2 =  1.133E+01
>       iter #   5 total cpu time :   210.5 secs   av.it.:   4.8
>       thresh= 1.000E-02 alpha_mix =  0.400 |ddv_scf|^2 =  3.608E+00
>       iter #   6 total cpu time :   227.5 secs   av.it.:   3.3
>       thresh= 1.000E-02 alpha_mix =  0.400 |ddv_scf|^2 =  4.009E+00
>       iter #   7 total cpu time :   256.9 secs   av.it.:   9.3
>       thresh= 1.000E-02 alpha_mix =  0.400 |ddv_scf|^2 =  6.845E+01
>       iter #   8 total cpu time :   277.9 secs   av.it.:   5.2
>       thresh= 1.000E-02 alpha_mix =  0.400 |ddv_scf|^2 =  4.813E+01
>       iter #   9 total cpu time :   297.8 secs   av.it.:   4.8
>       thresh= 1.000E-02 alpha_mix =  0.400 |ddv_scf|^2 =  1.080E+02


I've tried to reduce the alpha_nmix to 0.4 and 0.2 but it did not help.
The same calculation, with proper parameters but with pseudopotentials
without semicore states does not give any problem.
You can download the input and output file, as well as the pseudopotentials
at the following link

https://www.dropbox.com/sh/zw2db8q8loczz02/AACmax-Dby-9JqZjnm1QW_LWa?dl=0

Do you have any suggestions?
Thank you very much for your kind help!
Best,

Antonio Crepaldi-Lanza

-- Department of Physics "Aldo Moro" University of Bari
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