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

Christoph Wolf wolf.christoph at qns.science
Tue Nov 13 01:42:04 CET 2018

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!

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