[Pw_forum] Force is fluctuating for water system

[Ari P Seitsonen]

Dear Narendra Nath Ghosh,

   Adding to Lorenzo's answer, a small note: You seem to have an odd number 
of electrons but you do not specify 'nspin = 2' - are you sure that this 
is what you intended to do (physically)? 70 Ry with a pseudo potential à 
la Troullier-Martins for oxygen, it might be at the lower limit (it 
depends on the core radii, usually I would go for 80-90 Ry minimum). And, 
do you know if the electron gets localised or remains delocalised - this 
is an open question to my knowledge, and might well depend on the kind of 
exchange-correlation functional used (GGA like BLYP probably delocalise it 
- with the highest occupied orbital in the conduction band - and hybrid 
functionals might localise it).

     Greetings from Helsinki/Finland,

        apsi

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   Ari Paavo Seitsonen / Ari.P.Seitsonen at iki.fi / http://www.iki.fi/~apsi/
     Ecole Normale Supérieure (ENS), Département de Chimie, Paris
     Mobile (F) : +33 789 37 24 25    (CH) : +41 79 71 90 935


On Tue, 19 Dec 2017, Narendranath Ghosh wrote:

> Dear all 
> 
> I am relaxing a system of 128 water molecule with extra electron.The force is fluctuating even after bfgs
> steps   =  48.
> 
> 
> 
> Input:
> 
> &CONTROL
>   calculation='relax',
>   outdir='/share_home/hpc/NEGATIVE_HYDRATED_ELECTRON/OUTPUT',
>   prefix='water-128-negative',
>   pseudo_dir='/share_home/hpc/RESEARCH_SCHOLAR/HYDRATED-ELECTRON/pseudo',
>   verbosity='high',
>   restart_mode='restart',
> /
> &SYSTEM
>   ibrav=0,
>   celldm(1)=29.8576727681d0,
>   nat=384,
>   tot_charge=-1,
>   ntyp=2,
>   ecutwfc=70,
>   ecutrho=280,
>   input_dft='BLYP',
>   occupations='smearing',
>   degauss=0.05d0,
> /
> &ELECTRONS
>   mixing_beta=0.500d0,
>   electron_maxstep=500,
> /
> &IONS
> /
> ATOMIC_SPECIES
>  O  16.0d0   O.blyp-mt.UPF
>  H  1.0079d0 H.blyp-vbc.UPF
> 
> K_POINTS {automatic}
>   1 1 1 0 0 0
> CELL_PARAMETERS {alat}
>   1.000000000000d0  0.000000000000d0  0.000000000000d0
>   0.000000000000d0  1.000000000000d0  0.000000000000d0
>   0.000000000000d0  0.000000000000d0  1.000000000000d0
> 
> Output
> 
>     Total force =     0.030447     Total SCF correction =     0.001115
>      Total force =     0.033732     Total SCF correction =     0.000223
>      Total force =     0.042921     Total SCF correction =     0.000171
>      Total force =     0.032971     Total SCF correction =     0.000165
>      Total force =     0.032983     Total SCF correction =     0.000266
>      Total force =     0.036132     Total SCF correction =     0.000252
>        Total force =     0.040191     Total SCF correction =     0.000833
>      Total force =     0.032897     Total SCF correction =     0.001663
>      Total force =     0.025425     Total SCF correction =     0.000288
>      Total force =     0.019869     Total SCF correction =     0.000279
>      Total force =     0.020382     Total SCF correction =     0.000102
>      Total force =     0.025164     Total SCF correction =     0.000109
>      Total force =     0.027580     Total SCF correction =     0.000141
>      Total force =     0.026211     Total SCF correction =     0.000188
>      Total force =     0.023574     Total SCF correction =     0.000139
>      Total force =     0.024877     Total SCF correction =     0.000103
>      Total force =     0.027597     Total SCF correction =     0.000131
>      Total force =     0.027563     Total SCF correction =     0.000169
>      Total force =     0.023015     Total SCF correction =     0.000195
>      Total force =     0.021111     Total SCF correction =     0.000109
>      Total force =     0.021345     Total SCF correction =     0.000092
>      Total force =     0.023793     Total SCF correction =     0.000129
>      Total force =     0.024400     Total SCF correction =     0.000145
>      Total force =     0.025073     Total SCF correction =     0.000243
>      Total force =     0.022300     Total SCF correction =     0.000376
>      Total force =     0.020060     Total SCF correction =     0.000097
>      Total force =     0.021991     Total SCF correction =     0.000134
>      Total force =     0.022541     Total SCF correction =     0.000132
>      Total force =     0.023051     Total SCF correction =     0.000158
>      Total force =     0.023734     Total SCF correction =     0.000168
> 
> 
>      Total force =     0.023734     Total SCF correction =     0.000168
>      number of scf cycles    =  49
>      number of bfgs steps    =  48
>      energy   old            =   -4400.3520443575 Ry
>      energy   new            =   -4400.3528674259 Ry
>      CASE: energy  _new < energy  _old
>      new trust radius        =       0.0602516409 bohr
>      new conv_thr            =       0.0000000591 Ry
> 
> Please help me.
> 
> Dr. Narendra Nath Ghosh
> 
> Research Associate
> 
> University of Gour  Banga
> 
> Malda-732102
> 
> India
> 
> Phone No : 09126667601
> 
> 
>