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

[Nicola Marzari]

On 13/11/2018 01:42, Christoph Wolf wrote:
> Dear all,
> 


Last options would be alpha_mix and nmix_ph, while using a decent 
smearing (.02 Ry, when in doubt)?

Here it is: https://www.quantum-espresso.org/Doc/INPUT_PH.html#idm36

Your alpha_mix is small, so maybe you tried. What about smaller? More
iterations in nmix?

The only method bound to converge would be a direct minimization of the
variational functional for linear-response theory, but that would be 
major work to implement.


			nicola


> thank you for your help so far. Unfortunately I am still not able to 
> reach self consistency during the ph.x calculation. I have tested all 
> smearing methods (and tetrahedra_opt), several smearing widths between 
> 0.001 and 0.02, in-plane k-point grids up to 21x21x1 (121 k points) and 
> relaxed the structure down to forces of 1e-6 a.u..
> 
> whilst I can reach arbitrary scf accuracy
> 
> !    total energy              =   -3634.01568752 Ry
>       Harris-Foulkes estimate   =   -3634.01568752 Ry
>       estimated scf accuracy    <          5.9E-17 Ry
> 
> there seems to be no way to avoid the "oscillating" behavior in ph.x
>       Pert. #  1: Fermi energy shift (Ry) =    -9.6471E-02     0.0000E+00
> 
>        iter # 100 total cpu time : 23216.2 secs av.it <http://av.it>.:   7.2
>        thresh= 1.733E-04 alpha_mix =  0.100 |ddv_scf|^2 =  1.665E-09
>       End of self-consistent calculation
>       No convergence has been achieved
> 
> This is very odd and very frustrating - I am curious if anyone else has 
> encountered this for thin (7-11 ML) metal layers and has found a 
> strategy to overcome this?
> 
> Thanks in advance for your help, it is very much appreciated!
> 
> Best,
> Chris
> -- 
> Postdoctoral Researcher
> Center for Quantum Nanoscience, Institute for Basic Science
> Ewha Womans University, Seoul, South Korea
> 
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-- 
----------------------------------------------------------------------
Prof Nicola Marzari, Chair of Theory and Simulation of Materials, EPFL
Director, National Centre for Competence in Research NCCR MARVEL, EPFL
http://theossrv1.epfl.ch/Main/Contact http://nccr-marvel.ch/en/project