[Pw_forum] one layer calculations

Gabriele Sclauzero sclauzer at sissa.it
Mon Apr 20 09:57:51 CEST 2009


Mehrnaz Anvari wrote:
> Hello
> Thanks because of your attention.first I have to say, I couldn't 
> understand cell_dofree, I have celldm(1) & celldm(3) in my input, so how 
> could I insert cell_dofree. 

Well, it depends what you want to do... with so little of informations it's hard to guess.

> Second problem  is when I choose 
> celldm(3)=10 after vc-rx the calculated stress along z become 
> approximately zero & when I put celldm(3)=3 it reached stress=-2 (& it 
> means that my cell is large). 

Here the point is not clear at all? Where is the problem? The calculates stress depends on 
the cell parameters, but also on what you put inside of you cell. So you should specify 
what kind of system you are studying and a sample for an input file.

> I know for introducing one layer to system 
> I have to create vacuum in z so how could I choose the best value 
> between them?

If you want to create vacuum layers between surfaces in a slab geometry, I think you 
should not look at stress, but rather at the convergence of total energy as a function of 
the vacuum thickness.



> Best Regards
> Mehrnaz Anvari
> Iran University Of Science & Technology 
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