[QE-users] DFPT of thin metal layer: convergence has not been achieved

[Christoph Wolf]

Dear all,

I am trying to calculate the phonon spectrum for a series of thin metal
layer. However there seem to be a few "pathological" cases such as Cu(111)
where, no matter what, I cannot achieve convergence during the ph.x
calculation.

I have tried, to no avail, change mixing parameter, k point sampling,
ecutrho, ecutwfc, smearing type, occupation type, ...

If someone has a hint on how to tackle this I would be entirely grateful. I
know it can be done as there are a few works out there focusing on thin
metal film phonons but non of them has additional information.

The general setup is 11 layers of metal padded by 20A of vacuum. I
generated the layers using "thermo_pw" and I manually and meticulously
checked bond lengths and residual forces on the atoms after relaxation
(<1e-6).

Any help is very welcome!

Thanks in advance and with best regards,
Chris

-- 
Postdoctoral Researcher
Center for Quantum Nanoscience, Institute for Basic Science
Ewha Womans University, Seoul, South Korea
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