[Pw_forum] how to do fixed volume optimization

[Ngoc Linh Nguyen]

Kun Yin wrote:
> 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
>   
Why don't you build a supercell that stores the considering structure.
When you do optimization, the volume of supercell will be fixed , but 
the structure is still optimized.

Hope this help.

Linh
> ------------------				 
> 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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>>     
>
>
>
>   


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