[Pw_forum] Large shift of the Fermi energy - phonons, slab

[Andrea Dal Corso]

On Sun, 2013-10-27 at 19:04 +0100, Nicki Frank Hinsche wrote:
> Dear community, 
> 
> 
> I am puzzled with some non-converging phonon calculations and
> especially with a very large shift of the Fermi energy in the
> perturbation step. 
> I am doing some calculations on metallic slabs, comparable to Eiguren
> et al. Phys. Rev. Lett. (2002) vol. 88 (6) 066805 or 
> Hofmann et al. New Journal of Physics (2009) vol. 11 (12) 125005. It
> worked out for several systems, with various thicknesses but now I
> become 
> desperate calculating the phonons of a simple 21layer slab of Cu(111).
> The vac. is around 2.5nm. The electronic structure looks fine, the
> relaxation 
> is done - but the phonons fail for the Gamma point (only). The Fermi
> energy shift is unphysically large. The DOS has no resonance nearby. 
> 
> 
> So what could be the problem? Any hints would be helpful. 
> 
Please note that the phonon code is not working in versions 5.0 up to
5.0.2. You need to patch 5.0.2 to obtain 5.0.3.

Andrea


> 
> Thanks Nicki
> 
> 
> following some input/output for the phonons on (away) the Gamma point:
> 
> 
> Input:
> 
> 
> &inputph
>   reduce_io = .false.
>   tr2_ph=1.0d-12,
>   prefix='Cu',
>   alpha_mix = 0.150
>   ldisp=.true.,
>   nq1=4, nq2=4, nq3=1
>   start_q=1
>   last_q=1
>   recover = .true.,
>   amass(1)=63.546
>   outdir="***",
>   fildyn='Cu.dyn',
>  /
> 
> 
> Output Gamma:
> 
> 
> Computing dynamical matrix for.
>                     q = (   0.0000000   0.0000000   0.0000000 )
> 
> 
>       7 Sym.Ops. (with q -> -q+G )
> //
> Atomic displacements:
>      There are  42 irreducible representations
> //
>  Representation #  1 mode #   1
> 
> 
>      Self-consistent Calculation
> 
> 
>      Pert. #  1: Fermi energy shift (Ry) =    -0.1403E+01
>  -0.8470E-21
>      
>       iter #   1 total cpu time :   168.5 secs   av.it.:   6.1
>       thresh= 0.100E-01 alpha_mix =  0.150 |ddv_scf|^2 =  0.277E+00
> //
>       Pert. #  1: Fermi energy shift (Ry) =     0.1555E+08
>  -0.8882E-15
> //
>       iter # 100 total cpu time :  2038.3 secs   av.it.:  25.3
>       thresh= 0.100E-01 alpha_mix =  0.150 |ddv_scf|^2 =  0.313E+15
> 
> 
> 
> 
> And the output for a q-point away from Gamma:
> 
> 
> Computing dynamical matrix for.
>                     q = (   0.1443376   0.2500000   0.0000000 )
> 
> 
>       2 Sym.Ops. (no q -> -q+G )
> //
>  Atomic displacements:
>      There are  63 irreducible representations
> //
> Representation #  1 mode #   1
>      
>      Self-consistent Calculation
> 
> 
>       iter #   1 total cpu time :  1117.1 secs   av.it.:   5.8
>       thresh= 0.100E-01 alpha_mix =  0.150 |ddv_scf|^2 =  0.315E-04
> //
>       iter #  15 total cpu time :  2442.8 secs   av.it.:  10.2
>       thresh= 0.105E-06 alpha_mix =  0.150 |ddv_scf|^2 =  0.454E-12
> 
> 
> 
> 
> 
> 
> Some info on the self-consistent calculation before:
> 
> 
> occupations='smearing', smearing='methfessel-paxton', degauss=0.01
> ecutwfc = 38.0, ecutrho = 304.0,
> conv_thr =  1.0d-10
> K_POINTS {automatic}: 12 12 1 0 0 0
> nat= 21, ntyp= 1
> CELL_PARAMETERS {hexagonal}
> 0.86602540    -0.5000000   0.000000
> 0.86602540    0.50000000   0.000000
> 0.00000000    0.00000000   25.71450
> 
> 
> 
> 
> 
> 
> -------------------------------------------------------------
> Nicki Frank Hinsche, Dr. rer. nat.
> Institute of physics - Theoretical physics,
> Martin-Luther-University Halle-Wittenberg,
> Von-Seckendorff-Platz 1, Room 1.07
> D-06120 Halle/Saale, Germany
> Tel.: ++49 345 5525460
> -------------------------------------------------------------
> 
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-- 
Andrea Dal Corso                    Tel. 0039-040-3787428
SISSA, Via Bonomea 265              Fax. 0039-040-3787249
I-34136 Trieste (Italy)             e-mail: dalcorso at sissa.it