[Pw_forum] Pressure-induced phase transition

[Hongsheng Zhao]

On 07/19/2011 09:23 AM, Eric Germaneau wrote:
> Hey Amin,
>
> The approach you proposed is ok but you should relax the cell as well.
> By keeping the cell fix the system does not feel the pressure you wish
> to apply.

Not so clear about the meaning of this sentence, could you please give 
some more explanations? ;-(

> You can also change the volume, relax the positions only and compute the
> pressure.
> The best is to compute the free energy as function of pressure ans so
> the QHA method is the best way to go.

I think this method cann't do the job of structure-searching-and-finding 
for unknown phases when we changing the external pressure.

Regards

> Note that at first you can ignore the thermal effect and compute the
> free energy from a regular phonon calculations.
> I'm also very interested in such calculations but don't have experiences
> doing this by mean of first principal calculations.
>
> I hope that helps,
> Good luck,


-- 
Hongsheng Zhao <zhaohscas at yahoo.com.cn>
School of Physics and Electrical Information Science,
Ningxia University, Yinchuan 750021, China