[Pw_forum] problem on phonon

Stefano de Gironcoli degironc at sissa.it
Sat May 28 18:06:23 CEST 2011

Dear Bhabya Sahoo,

    your very stingy use of punctuation make quite difficult (at least 
for me) to follow your request...
    Take your time and try to make you clear providing more detailed 
information about your system, what is your aim, what is the problem, 
what are the tests you have done.
    No one is going to spend more time in thinking about your problem 
than you do in explaining it.

    Please provide your affiliation.

  Stefano de Gironcoli, SISSA and DEMOCRITOS

On 05/28/2011 05:46 PM, bhabya sahoo wrote:
> i am using quantum espresso static calculation obeys thermdyanamic stability
> transition from B1 to B2 transition at 138 gpa  so ihave used 24 24 24
> kpoint grid  for phonon in B2 phase is calculated 4 4 4 grid by linear
> response calculation but why the instability (negative frequency in phonon )
> upto 450 gpa  i have used pbe psudo potentials also the lattice constant is
> exact for experimental data
>   can metastability have negative frequency so why this occures
> optimisation is ok
> other problem why free energy is not coming for unstable phase for qha code
> in quantum espresso
> replay immidiate if u have solution
> On Sat, May 28, 2011 at 5:38 PM, bhabya sahoo<bdslipun at gmail.com>  wrote:
>> sir
>> i  used to calculate the phonon calculation on a 4*4*4 grid in cscl phase
>> but the unstability persists upto 500 gpa
>> but it is the thermodyanamic stability after 140 gpa  kpoints 24*24*24
>> what may be reseon i donot know
>> please help me
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