[Pw_forum] how to do fixed volume optimization

[Kun Yin]

Thanks for your reply, Mohnish. 
The 'relax' calculation will keep the volume constant but it will fix the cell parameters, too. For example, if I optimize a tetragonal cell,  I want the c and a axis to change but the volume unchanged. I know this could be done by varing c/a ratio manually with a series of relax calculation. My question is, can this be done automatically in QE?

------------------				 
Kun Yin
2010-05-30

Dear Yin 'vc-relax'  calculation optimizes the structures by the lattice
parameters also but if you set the calculation 'relax' then it optimizes the
geometry within the given fixed volume constraints. This calculation moves
the atom keeping the volume constant within the given symmetry constraint.
hope this helps :)

On Sun, May 30, 2010 at 6:12 PM, Kun Yin <kyin.cn at gmail.com> wrote:

> Dear All,
>
> Does anyone have the experience to do volume fixed optimization with QE,
> which means the structure is optimized allowing all cell parameters and
> atomic positions to vary while keeping the volume fixed?
>
> Kun Yin
> Najing University, China
> 2010-05-30
>
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-- 
Regards,
MOHNISH,
-----------------------------------------------------------------
Mohnish Pandey
Y6927262,4th Year dual degree student,
Department of Chemical Engineering,
IIT KANPUR, UP, INDIA
+919235721300
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