[QE-users] [SPAM] How to deal with a mode of phonon spectrum that cannot converge

[Lorenzo Paulatto]

On 15/03/2023 07:14, zhouchao via users wrote:
> How to deal with a mode of phonon spectrum that cannot converge, how 
> to make it converge, tried many methods, but can not be solved。
> how to explain this problem, what is the reason, is it a problem of 
> the structure itself, how to analyze it?

This output line give a suggestion:

Possibly too few bands at point    1   0.00000   0.00000   0.00000

your scf calculation has been done with 23 electronic bands (Kohn-Sham 
states), but it may not be enough for the phonon caculaiton. Try to 
increase this value a bit in the pw.x input

You can also try to increase nmix_ph, as hinted in the manual, to 20.

Finally, you can and decrease alpha_mix, and add a few more iterations 
of mixing, i.e.

alpha_mix = 0.3, 0.1, 0.05, 0.01


hth



> As shown in the end of the attachment, the first 10 modes all 
> converge, but the 11th mode fails to converge.
>
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-- 
Dr. Lorenzo Paulatto
IdR @ IMPMC - CNRS UMR 7590 & Sorbonne Université
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