[Pw_forum] Particular Phonon mode

[Gabriele Sclauzero]

Bipul Rakshit wrote:
> Dear PWscf users,
> I am doing gamma Phonon calculation on LaMnO3. Since the unit cell 
> contain 20 atoms, so at gamma i am getting 60 frequencies (3 acoustic 
> modes ~ 0)
> 
> If I am just interested in just the first three frequencies ( the 
> acoustic modes), what changes i have to made in the input file.

You could try to specity nrapp=1 in the namelist and add a line containing the index of 
the representation you are interested in. I suppose that acoustic modes should be done 
first and should fall in one single representation, so that you can add
  1

at the end of the input file.
I'm not sure if this is the correct way, so look carefully to what you will obtain on output.

HTH

GS


> 
> phonons of LaMnO3-pero
>  &inputph
>   tr2_ph=1.0d-10,
>   alpha_mix(1)= 0.7,
>    prefix='lamno3',
> !  epsil=.true.,
> !  ldisp=.true.,
> !  nq1=2, nq2=2, nq3=2
> !  iq1=6, iq2=6, iq3=6
> !   lnscf= .true.
>   amass(1)= 138.9055,
>   amass(2)=54.938049,
>    amass(3)=15.9994, 
>   outdir = './OUT',
>   fildyn='LaMnO3.dynG',
>  /
>  0.0 0.0 0.0
> 
> -- 
> Dr. Bipul Rakshit
> Research Associate,
> S N Bose Centre for Basic Sciences,
> Salt Lake,
> Kolkata 700 098
> India
> 
> 
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