[Pw_forum] phonon calculation

[xirainbow]

Dear Banafshe Noori :

> can i use of press_conv_thr   for a relax of phonon calculation?
            What is "relax of phonon calculation"? You can even do
phonon with experimental crystal lattices and atomic positions without
any relaxation.

> and why the stress on my system is too high?(-40kbar)
           Take the output structure of pw.x as an input and relax it
again and again.

> What parameters do I need to be changed to reduce stress?
            Reduce press_conv_thr.

On Sun, Jun 2, 2013 at 2:36 PM, Banafshe Noori <b_noori88 at yahoo.com> wrote:
> Dear Xirainbow
>
> thank alot for your respond.
>
> I search in the input file of pwscf and saw that the is applied for a
> vc-relax calculation.
> can i use of press_conv_thr   for a relax of phonon calculation?
> and why the stress on my system is too high?(-40kbar)
> What parameters do I need to be changed to reduce stress?
>
>
>
>
>
> Dear Banafshe Noori :
>             press_conv_thr is the parameter to control the final stress.
>             The default value for press_conv_thr is  0.5D0 Kbar, which
> is good enough for most condition.
>
> On Sat, Jun 1, 2013 at 11:45 PM, Banafshe Noori <b_noori88 at yahoo.com> wrote:
>> Dear all
>>
>> I want to calculate phonon frequency. I did a relax for my system(carbon
>> nanotube) and saw that  the stress (Kbar) for this system is around
>> (-40Kbar). How can i decrease the stress on my system, and for an
>> acceptable
>> magnitude of ferquencey,  how much be the stress on system.?
>>
>
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-- 
____________________________________
Hui Wang
School of physics, Fudan University, Shanghai, China