[Pw_forum] Total forces of relaxing metallic system decreases then increases gradually

[Hind Almisbahi]

Dear stefano,

Thank you for your reply. Yes the energy is decreasing but I aborted the
run after 14 scf cycles. I will repeat the run with the norm conserving
potential and wait until it finish.


Best Regards,
Hind
Lecturer
IT department
King Abdulaziz University

On Sun, Feb 18, 2018 at 10:12 AM, Stefano de Gironcoli <degironc at sissa.it>
wrote:

> is the energy decreasing ? if so the relaxation is not yet finished.
>
> stefano
>
> On 18/02/2018 02:55, Hind Almisbahi wrote:
>
> Dear experts of quantum espresso,
>
> I am doing relaxation and the problem is that the total force is
> decreasing until the 4th scf, then start to increase gradually. The
> system does not converge. Actually, I need to calculate the band structure
> and see the band gap of Armchair graphene ribbon. The ribbon width is
> composed of 17 carbon atoms (N=3p+2 family), so it is metallic. I have one
> unit cell of the ribbon. I read in this mailing list many useful
> discussions about suitable input for metallic systems and I followed them
> as I understand. The version of quantum espresso is 6.1.
>
> I tried many options of the input script but all the runs have the same
> problem, total force is decreasing until the 4th scf then start to
> increase gradually. This is a complete version of my input:
>
>
>
> &CONTROL
>
>   calculation='relax',
>
>   outdir='.\Work',
>
>   prefix='Arm17',
>
>   pseudo_dir='C:\qe-6.1\pseudo',
>
>   verbosity='high',
>
>   etot_conv_thr= 1.0D-3,
>
>   forc_conv_thr=1.0d-2,
>
> /
>
> &SYSTEM
>
>   ibrav=8,
>
>   a=41.1089d0,
>
>   b=4.26258d0,
>
>   c=20.0d0,
>
>   nat=34,
>
>   ntyp=1,
>
>   ecutwfc=65,
>
>   ecutrho=520,
>
>   nbnd=76
>
>   occupations='smearing',
>
>   smearing='marzari-vanderbilt',
>
>   degauss=0.001d0,
>
> /
>
>
>
> &ELECTRONS
>
>   conv_thr=1d-06,
>
>   mixing_beta=0.7d0,
>
>   mixing_mode='local-TF'
>
>   mixing_ndim=12
>
>   diagonalization='cg'
>
> /
>
>
>
> &IONS
>
> /
>
>
>
> ATOMIC_SPECIES
>
>   C 12.010700d0 C.pbe-rrkjus.UPF
>
>
>
> ATOMIC_POSITIONS {crystal}
>
>    C   0.0336555229d0   0.6666666956d0   0.5000000000d0
>
>    C   0.0919486003d0   0.8333333913d0   0.5000000000d0
>
>    C   0.0336555229d0   0.3333333044d0   0.5000000000d0
>
>    C   0.1502416777d0   0.6666666956d0   0.5000000000d0
>
>    C   0.2085347551d0   0.8333333913d0   0.5000000000d0
>
>    C   0.0919486003d0   0.1666666087d0   0.5000000000d0
>
>    C   0.1502416777d0   0.3333333044d0   0.5000000000d0
>
>    C   0.2668277852d0   0.6666666956d0   0.5000000000d0
>
>    C   0.3251206731d0   0.8333333913d0   0.5000000000d0
>
>    C   0.2085347551d0   0.1666666087d0   0.5000000000d0
>
>    C   0.2668277852d0   0.3333333044d0   0.5000000000d0
>
>    C   0.3834141768d0   0.6666666956d0   0.5000000000d0
>
>    C   0.4417072068d0   0.8333333913d0   0.5000000000d0
>
>    C   0.3251206731d0   0.1666666087d0   0.5000000000d0
>
>    C   0.3834141768d0   0.3333333044d0   0.5000000000d0
>
>    C   0.5000002369d0   0.6666666956d0   0.5000000000d0
>
>    C   0.5582932669d0   0.8333333913d0   0.5000000000d0
>
>    C   0.4417072068d0   0.1666666087d0   0.5000000000d0
>
>    C   0.5000002369d0   0.3333333044d0   0.5000000000d0
>
>    C   0.6165862969d0   0.6666666956d0   0.5000000000d0
>
>    C   0.6748793269d0   0.8333333913d0   0.5000000000d0
>
>    C   0.5582932669d0   0.1666666087d0   0.5000000000d0
>
>    C   0.6165862969d0   0.3333333044d0   0.5000000000d0
>
>    C   0.7331723570d0   0.6666666956d0   0.5000000000d0
>
>    C   0.7914653870d0   0.8333333913d0   0.5000000000d0
>
>    C   0.6748793269d0   0.1666666087d0   0.5000000000d0
>
>    C   0.7331723570d0   0.3333333044d0   0.5000000000d0
>
>    C   0.8497584170d0   0.6666666956d0   0.5000000000d0
>
>    C   0.9080514470d0   0.8333333913d0   0.5000000000d0
>
>    C   0.7914653870d0   0.1666666087d0   0.5000000000d0
>
>    C   0.8497584170d0   0.3333333044d0   0.5000000000d0
>
>    C   0.9663444771d0   0.6666666956d0   0.5000000000d0
>
>    C   0.9080514470d0   0.1666666087d0   0.5000000000d0
>
>    C   0.9663444771d0   0.3333333044d0   0.5000000000d0
>
>
>
> K_POINTS {automatic}
>
> 1       50  1  0  0  0
>
>
>
> These are some of the many options that I have explored:
>
> The above potential is ultrasoft, I used also norm conserving
> (C.pbe-mt_gipaw.UPF).
>
> Smearing: I used methfessel-paxton and marzari-vanderbilt
>
> Degause: I used 0.01 and 0.001
>
> mixing_beta: I used 0.1 and 0.7
>
> mixing_mode: I used local-TF and TF
>
> mixing_ndim: I used 8 and 12
>
> diagonalization: I used cg and david
>
> ecutwfc: I used 65 and 75
>
> ecutrho: with norm conserving (ecutwfc*4 and ecutwfc*10), with ultrasoft
> (ecutwfc*8)
>
> nbnd=76 (I have 34 atoms, so 136 valence electrons which need 68 bands,
> because it is metallic I added 8 extra bands)
>
> Previously I have successfully calculated the band structure and band gap
> of semiconductor ribbon but I could not do the calculation of metallic
> ribbon. I appreciate any help to solve my problem, why the forces always
> increase after the 4th scf?
>
> ​
>
> Best Regards,
>
> Hind
>
> Lecturer, IT department
>
> King Abdulaziz University
>
>
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