[Pw_forum] convergence stops after 100 iterations

[Nguyen Chuong]

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
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20131224/e433a187/attachment.html>