[Pw_forum] optimization

[Axel Kohlmeyer]

On Sun, 6 May 2007, ali kazempoor wrote:

ali,

please note, that there is no 'ultimate wisdom' on
how to setup a specific calculation. you usually have 
to run a few tests and figure it out for yourself (i.e.
everybody has, with some experience people can make good
guesses, but that does not mean, they have to test it). 
what may work well in one case may produce (large) errors 
in other cases.

please have a look through the mailing list archives
and see the various recommendations on how to approach
finding out the proper supercell size, number of k-points,
smearing parameter, wavefunction/density cutoff. 
all of which can affect the quality of your results.

for people with limited experience (either with the system
they are investigating or the method altogether), it is 
usually a good idea to first try to reproduce results from
some other, similar but (computationally) much simpler system
and then try to understand why which parameter works in its
special way and what influences the accuracy. you can see 
quite a few of that kind of questions here in the archives.
so don't hesitate to ask if you have a question about a
particular detail, but don't expect that somebody will
eplain your whole project to you, or simply give you
his 'blessing' on your inputs.

best regards,
    axel.

AK> Hi
AK>  i make super cell that
AK> its situation is in the center of big tetragonal cell
AK>   and has hexagonal (wurtzite structure),
AK> but i dont  know about the number of k-point, vaccum
AK> and other detail 
AK> if you can ,help me in these subject.(i attach my
AK> input file)
AK> thank you 
AK> regards
AK> 
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-- 
=======================================================================
Axel Kohlmeyer   akohlmey at cmm.chem.upenn.edu   http://www.cmm.upenn.edu
   Center for Molecular Modeling   --   University of Pennsylvania
Department of Chemistry, 231 S.34th Street, Philadelphia, PA 19104-6323
tel: 1-215-898-1582,  fax: 1-215-573-6233,  office-tel: 1-215-898-5425
=======================================================================
If you make something idiot-proof, the universe creates a better idiot.