[Pw_forum] Improve convergence, slab and electric field.

[Guda Karthik]

Your ecutwfc is too low. Check that. and ecutrho should be 8-10 times
ecutwfc. The celldm(1) cannot be 1.0. What are the units? check that.

On Fri, Aug 27, 2010 at 11:29 AM, joaquin peralta <jperaltac at gmail.com>wrote:

> Dear pw_forum
>
> I try to simulate a metallic slab under a electric field. In order to
> improve the convergence, I checked this web page :
>
> http://blog.sina.com.cn/s/blog_5f15ead20100cw4d.html
>
> I tried all the suggestion (except band number increase) and the process
> continue with a very slow convergence, after 283 iterations the ethr=1.2E-9.
> The important part of the input file is :
>
> &CONTROL
>    calculation           = 'scf'
>    ...
>    tefield               = .true.
>    dipfield              = .true.
> /
> &SYSTEM
>    ibrav                 =  0
>    celldm(1)             =  1.0
>    nat                   = 21
>    ntyp                  = 1
>    ecutwfc               = 30
>    ecutrho               = 500
>    degauss               = 0.03
>    occupations           = 'smearing'
>    smearing              = 'mv'
>    nspin                 = 2
>    starting_magnetization= 0.1
>    edir                  = 3
>    emaxpos               = 0.9
>    eopreg                = 0.2
>    eamp                  = 0.019447
> /
> &ELECTRONS
>    electron_maxstep      = 300
>    mixing_mode           = 'local-TF'
>    mixing_beta           = 0.1
>    mixing_ndim           = 10
> /
> ...
> K_POINTS (automatic)
> 6 6 6 0 0 0
> ...
> This process use approx 5Gb of data in the associated files.
>
> My question are,
> -If I increase the band number, The space disk will be more?
> -Do you have suggestion about how to proceed in order to avoid this I/O
> increase. and improve the convergence or velocity.
> -I'm (over/under)estimating some previous value?, k-points, mixing_*,
> ecut*?
>
> Thanks in advance
> Joaquin Peralta
> Materials Science and Engineering
> Iowa State University.
>
> --
> ----------------------------------------------------
> Group of NanoMaterials
> ----------------------------------------------------
> http://www.gnm.cl
> ----------------------------------------------------
> Joaquín Andrés Peralta Camposano
> ----------------------------------------------------
> http://www.lpmd.cl/jperalta
>
> In a world without frontiers,
> who needs Gates and Win.
>
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>


-- 
Karthik Guda
Graduate Student
Materials Engineering
Purdue University
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