[Pw_forum] phonon calculation

[Banafshe Noori]

Dear Xirainbow:
Thank you very much for your reply.
What is "relax of phonon calculation?
My purpose was the relax calculation before doing calculation of frequency.


Message: 1Date: Sun, 2 Jun 2013 19:07:20 +0800

From: xirainbow <nkxirainbow at gmail.com>

Subject: Re: [Pw_forum] phonon calculation

To: Banafshe Noori <b_noori88 at yahoo.com>, PWSCF Forum

    <pw_forum at pwscf.org>

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    <CABBv2WJG3M5aiQc_nsSi6BcebE4oF2_yop42qNEs0Jrz-9vJ1Q at mail.gmail.com>

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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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