[Pw_forum] vc-relax or relax

[Lorenzo Paulatto]

In data 20 agosto 2009 alle ore 14:27:40, ali kazempour  
<kazempoor2000 at yahoo.com> ha scritto:
> I make 72 atom supercell to study the effect of vacancy on defect  
> formation energy. If I remove one atom do I run vc-relax or relax  
> calculation only? I mean is this concentratio(1/72=0.013) high that  
> affect  the lattice constant also or not?

Dear Ali,
it is difficult to say, you can do a normal relax and print the pressure  
in order to see if it is low enough. It would also be interesting to know  
which is the vacancy concentration in the real system you are trying to  
simulate: is it 1/72 or is it much lower? In the latter case, you should  
definitely keep the cell parameter fixed.

best regards

-- 
Lorenzo Paulatto
SISSA  &  DEMOCRITOS (Trieste)
phone: +39 040 3787 511
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