[Pw_forum] optimization of any structure

[Prasenjit Ghosh]

Dear Sathya,

I have no experience in using 'vc-relax'.......so I can't help you out on
this. Either you wait for other people's comments or you can search the pw
forum mailing list. There were discussions regarding this earlier in this
forum. I said its tricky because you need to choose different parameters
correctly to reach the minima quickly and correctly. What I would suggest is
to play around with different parameters for some small system and
understand how they affects the calculation. Later you can go for production
run.

Prasenjit.

2008/7/30 sathya subramanyan <sathya_sheela1985001 at rediffmail.com>

>
> Dear Dr. Prasenjit,
>                     Thank you so much for your reply and the link.
>                   I'm doing the vc-relax calculation but it has been
> running for more than 36 hours.Is this why you have mentioned that vc-relax
> is tricky ? I have attached the I/P file for reference and if you could
> please take a look at it.
>                   I'm also trying the manual relaxation and will let you
> know the status of my results.
>
> INPUT FILE FOR VC-RELAX
>
> &CONTROL
>   calculation =  "vc-relax"  ,
>   restart_mode = 'from_scratch' ,
>   outdir='/home/413107002/tmp/' ,
>   pseudo_dir = '/home/413107002/espresso-4.0.1/pseudo' ,
>   nstep =  1000  ,
>               etot_conv_thr = 1.0E-10  ,
>               forc_conv_thr = 1.0D-10 ,
>                           dt = 150 ,
> /
> &SYSTEM
>   ibrav = 6 ,
>   celldm(1)=7.373 ,
>   celldm(3)=1.065,
>     nat  = 5 ,
>     ntyp  =  3 ,
>     ecutwfc  = 30.0,
>     ecutrho  =  300.0 ,
>     occupations  =  'fixed' ,
>     degauss  =  0.00 ,
> /
> &ELECTRONS
>                     conv_thr  =  1.0d-10  ,
>             diagonalization  =  'david'  ,
> /
> &IONS
>   ion_dynamics = 'damp'
> /
> &CELL
>   cell_dynamics = 'damp-w' ,
>
> /
> ATOMIC_SPECIES
>   Pb  207.2    Pb.vdb.UPF
>   Ti  47.867  Ti.vdb.UPF
>   O    15.9994  O.vdb.UPF
> ATOMIC_POSITIONS
> Pb    0.000    0.000    0.000
> Ti    0.500    0.500    0.538
> O    0.500    0.000    0.612
> O    0.000    0.500    0.612
> O    0.500    0.500    0.117
> K_POINTS {automatic}
>   4 4 4  1 1 1
>
> Thanking you,
> SATHYA SHEELA.S
> Grad. Student
> Department of Physics
> National Institute of Technology
> Tiruchirapalli - 620015
> India
>
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-- 
PRASENJIT GHOSH,
POST-DOC,
ROOM NO: 265, MAIN BUILDING,
CM SECTION, ICTP,
STRADA COSTERIA 11,
TRIESTE, 34104,
ITALY
PHONE: +39 040 2240 369 (O)
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