[Pw_forum] convergence stops after 100 iterations

[Nguyen Chuong]

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
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>



-- 
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
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