[Pw_forum] Difficulties with scf convergence

[Masoud Nahali]

Dear *Никита Вакула

*

Have you tried the calculation considering spin polarization, nspin=2 and
checking the convergence ?

you can try a smaller degauss value using marzari-vanderbilt or gaussian
too.
Please check the smearing energy contribution to your total energy.


Are the interface atoms in close distances from each other ? I mean 1.2-2.0
angstrom for instance. If not and you put them at far distances from each
other you may relax a van der Waals interaction in which the pure DFT is
weak.

Do you really need such high amount of cutoff for energy and density ?

I hope it helps.







Best Wishes, m





----------------------------------------
Masoud Nahali
SUT
masoud.nahali at gmail.com
alum.sharif.edu/~m_nahali




On Mon, Apr 8, 2013 at 12:00 PM, *Никита Вакула* wrote:

>
>   Hi everybody,
>
> I am trying to optimize the structure of an interface between metal and
> insulator but have difficulties with scf convergence. Here are the changes
> in energies during scf cycle:
> estimated scf accuracy < 17.58555120 Ry
> estimated scf accuracy < 14.17435383 Ry
> estimated scf accuracy < 2.05765892 Ry
> estimated scf accuracy < 2.09375911 Ry
> estimated scf accuracy < 1.37675281 Ry
> estimated scf accuracy < 0.42594758 Ry
> estimated scf accuracy < 0.29104539 Ry
> estimated scf accuracy < 0.51143695 Ry
> estimated scf accuracy < 0.18765814 Ry
> estimated scf accuracy < 0.92590998 Ry
> estimated scf accuracy < 0.93126088 Ry
> estimated scf accuracy < 0.44023978 Ry
> estimated scf accuracy < 0.33756785 Ry
> estimated scf accuracy < 0.34216551 Ry
> estimated scf accuracy < 0.36573444 Ry
> estimated scf accuracy < 0.29089342 Ry
> estimated scf accuracy < 0.29287805 Ry
> estimated scf accuracy < 0.16940331 Ry
> estimated scf accuracy < 0.17503222 Ry
> estimated scf accuracy < 0.09708451 Ry
> estimated scf accuracy < 0.07751341 Ry
> estimated scf accuracy < 0.06774554 Ry
> estimated scf accuracy < 0.15834930 Ry
> estimated scf accuracy < 0.12269823 Ry
> estimated scf accuracy < 0.12679734 Ry
> estimated scf accuracy < 0.08558475 Ry
> estimated scf accuracy < 0.04411767 Ry
> estimated scf accuracy < 0.04754042 Ry
>
> I found similar posts on the forum ?but it didn't solve the problem. I
> checked my structure with xcrysen...it seems to be ok. I am using USPP.
> Any help and suggestions would be greatly appreciated.
>
> Thanks
>
> Here is my input:
> &CONTROL
> title = interface ,
> calculation = 'relax' ,
> restart_mode = 'from_scratch' ,
> wf_collect = .true. ,
> outdir = 'interface/' ,
> pseudo_dir = './' ,
> prefix = 'interface' ,
> lkpoint_dir = .true. ,
> disk_io = 'high' ,
> verbosity = 'high' ,
> nstep = 100 ,
> tstress = .false. ,
> tprnfor = .true. ,
> /
> &SYSTEM
> ibrav = 8,
> celldm(1) = 9.3957,
> celldm(2) = 1.7321,
> celldm(3) = 6.0000,
> nat = 72,
> ntyp = 3,
> ecutwfc = 50 ,
> ecutrho = 500 ,
> nbnd = 500,
> occupations = 'smearing' ,
> degauss = 0.025 ,
> smearing = 'methfessel-paxton' ,
> nspin = 1 ,
> /
> &ELECTRONS
> electron_maxstep = 200,
> conv_thr = 1.0d-6 ,
> mixing_mode = 'local-TF' ,
> mixing_beta = 0.1 ,
> mixing_ndim = 8 ,
> /
> &IONS
> ion_dynamics = 'bfgs' ,
> /
> ATOMIC_SPECIES
> ? BR,
>
> N V
>
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