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

[Christoph Wolf]

Dear all,

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.:   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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