[Pw_forum] convergence stops after 100 iterations

[manchugh at iitk.ac.in]

Hi Nguyen Chuong

I have used PBE (GGA)
electron_maxstep in my calculations is 100 by default. It means 1 scf
cycle will take 100 iterations at max,  nstep = 100 means number of ionic
+ electronic steps. It does not mean convergence will stop after 100
iterations.
I have convergence problem with different vacuum gaps but same number of
atoms in two cases I mentioned in my previous post.. why so ?

thanks

 Manjusha
 Research Scholar
 Department of Chemistry
 Indian Institute of Technology,Kanpur
 India

> and I have a question, in your file, which method you used for
> calculation?
> PBE (GGA) or PZ (LDA)
>
>
> On Tue, Dec 24, 2013 at 5:30 AM, Nguyen Chuong
> <chuongnguyen11 at gmail.com>wrote:
>
>> in your input file, nstep = 100, its mean convergence  will stopping in
>> 100 iterations.
>>
>>
>> On Tue, Dec 24, 2013 at 3:30 AM, <manchugh at iitk.ac.in> wrote:
>>
>>> Hi Quantum Espresso users
>>>
>>> I am trying to perform 'relax' calculations of GaN surface and trying
>>> to
>>> optimize the vacuum gap keeping the slab thickness same. One side of
>>> the
>>> slab (the N-terminated one) is passivated by pseudohydrogens of charge
>>> 0.75. For some values of the vacuum gap, relaxation proceeded
>>> successfully, (got Final energy in 12 scf cycles) but for some other
>>> values of vacuum gap, the 100 iterations in the Ist scf cycle itself
>>> are
>>> not sufficient and the following error appears:
>>>
>>> convergence NOT achieved in 100 iterations: stopping
>>>
>>> I am using  espresso-5.0.2 and my input file is as follows :
>>>
>>> &CONTROL
>>>     calculation = "relax",
>>>     title = '1x1x4_7gap'
>>>     verbosity = 'high',
>>>     restart_mode = 'from_scratch',
>>>     prefix = '1x1x4_7'
>>>     pseudo_dir = '/home/.....',
>>>     outdir = '/home/....../',
>>>     tprnfor = .TRUE.,
>>>     etot_conv_thr = 1.0D-04,
>>>     forc_conv_thr = 1.0D-03,
>>>     nstep = 100
>>>  /
>>> &SYSTEM
>>>     ibrav = 0 ,
>>>     celldm(1)= 6.088,
>>>     nat = 19 ,
>>>     ntyp = 3 ,
>>>     ecutwfc = 60.0 ,
>>>     ecutrho = 480.0 ,
>>>     input_dft = 'PBE' ,
>>>     occupations = 'smearing',
>>>     smearing = 'methfessel-paxton' ,
>>>     degauss = 0.05
>>>  /
>>>
>>> &ELECTRONS
>>>   diagonalization='cg',
>>>   conv_thr = 1.D-6,
>>>   mixing_mode = 'local-TF',
>>>   mixing_beta = 0.2D0
>>> /
>>>
>>> &IONS
>>>   ion_dynamics = 'bfgs'
>>> /
>>>
>>> CELL_PARAMETERS {hexagonal}
>>>  1.00  0.00   0.00
>>>  0.50  0.866  0.00
>>>  0.00  0.00   17.886
>>>
>>> ATOMIC_SPECIES
>>>   Ga  69.723  Ga.pbe-n-van.UPF
>>>   N   14.006  N.pbe-van_ak.UPF
>>>   H   1.0079  H.pz-vbc_075.UPF
>>>
>>> ATOMIC_POSITIONS {crystal}
>>> H   0.3333  0.3333  -0.029195     0  0  0
>>> N   0.3333  0.3333  -0.0111818    0  0  0
>>> Ga  0.000   0.000   0.000         0  0  0
>>> N   0.000   0.000   0.03427272
>>> Ga  0.3333  0.3333  0.04545454
>>> N   0.3333  0.3333  0.07972727
>>> Ga  0.000   0.000   0.09090909
>>> N   0.000   0.000   0.12518181
>>> Ga  0.3333  0.3333  0.13636363
>>> N   0.3333  0.3333  0.17063636
>>> Ga  0.000   0.000   0.18181818
>>> N   0.000   0.000   0.21609090
>>> Ga  0.3333  0.3333  0.22727272
>>> N   0.3333  0.3333  0.26154545
>>> Ga  0.000   0.000   0.27272727
>>> N   0.000   0.000   0.30699999
>>> Ga  0.3333  0.3333  0.31818181
>>> N   0.3333  0.3333  0.35245454
>>> Ga  0.000   0.000   0.36363636
>>>
>>> K_POINTS (automatic)
>>> 4  4  1  0  0  0
>>>
>>>
>>> For further information, this is a system with vacuum gap equivalent to
>>> 7
>>> GaN unit cells, the system with vacuum gap equivalent to 6 GaN unit
>>> cells
>>> worked fine. I am not getting why this problem is occurring only for
>>> few
>>> cases?
>>>
>>> Any kind of help or suggestions will be very valuable to me.
>>>
>>>
>>> Thanks
>>> -
>>> Manjusha
>>> Research Scholar
>>> Department of Chemistry
>>> Indian Institute of Technology,Kanpur
>>> India
>>> _______________________________________________
>>> Pw_forum mailing list
>>> Pw_forum at pwscf.org
>>> http://pwscf.org/mailman/listinfo/pw_forum
>>>
>>
>>
>>
>> --
>> Nguyen Van Chuong
>> PhD Student,
>> Department of Physics,
>> Don State Technical University.
>> Rostov on Don, Russia
>> Group Graphene
>> Email: chuongnguyen11 at gmail.com or cpuphys86 at gmail.com
>> Website: http://cpuphys86.webs.com/
>> Phone mobile: +7 905 45 94 888
>>
>>
>
>
> --
> Nguyen Van Chuong
> PhD Student,
> Department of Physics,
> Don State Technical University.
> Rostov on Don, Russia
> Group Graphene
> Email: chuongnguyen11 at gmail.com or cpuphys86 at gmail.com
> Website: http://cpuphys86.webs.com/
> Phone mobile: +7 905 45 94 888
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://pwscf.org/mailman/listinfo/pw_forum