[Pw_forum] Difficulties with scf convergence

[Никита Вакула]

 Dear Masoud,

thank you very much for your reply and suggestions. I haven't tried to use nspin=2 yet, but I will see if it helps. The distance between the atoms at the interface is around 2.5 angstrom.
I will let you know if your suggestions solves the problem.

Thanks!
BR,

NV


Понедельник,  8 апреля 2013, 16:03 +02:00 от Masoud Nahali <masoudnahali at gmail.com>:
>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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