# [Pw_forum] Reg: How to know the mode name and due to which atom it is happening?

Filipe Camargo Dalmatti Alves Lima flima at if.usp.br
Tue Apr 1 16:12:32 CEST 2014

It is because you did not finish all the steps to analyse the data.

I got a similar problem before and I remember it is possible to obtain a
file that has as the vectors of the modes that can be viewed in the
xcrysden. Unfortunately I don't run simulations phonon simulations anymore,
I couldn't remember everything I did in the past.

I am pasting a manual section that explains it in details. (I also change
the color to red the point I think might solve your issue.)

4.2 Calculation of interatomic force constants in real space

First, dynamical matrices are calculated and saved for a suitable uniform
grid of *q*-vectors (only those in the Irreducible Brillouin Zone of the
crystal are needed). Although this can be done one *q*-vector at the time,
a simpler procedure is to specify variable ldisp=.true. and to set
variables nq1, nq2,nq3 to some suitable Monkhorst-Pack grid, that will be
automatically generated, centered at [image: $\bf q$] = 0 .

Second, code q2r.x reads the dynamical matrices produced in the preceding
step and Fourier-transform them, writing a file of Interatomic Force
Constants in real space, up to a distance that depends on the size of the
grid of *q*-vectors. Input documentation in the header of PHonon/PH/q2r.f90.

*Program matdyn.x may be used to produce phonon modes and frequencies at
any q using the Interatomic Force Constants file as input. Input
documentation in the header of PHonon/PH/matdyn.f90.*

See Example 02 for a complete calculation of phonon dispersions in AlAs.

source:

I hope it will solve your issue.

Best regards,

Filipe

On Tue, Apr 1, 2014 at 8:49 AM, Peram sreenivasa reddy <
peramsreenivas at gmail.com> wrote:

> Dear xirainbow,
>
> Thank you very much for your replay.
>
> In that case.dyn1 file also it is giving same only as in the case.ph.out
> file.
>
> Please give me more clarification.
>
> Thanking you.
>
>
>
> On Tue, Apr 1, 2014 at 3:15 PM, xirainbow <nkxirainbow at gmail.com> wrote:
>
>> You can find the answer at the end of  *.dyn* files.
>>
>> On Mon, Mar 31, 2014 at 11:10 PM, Peram sreenivasa reddy
>> <peramsreenivas at gmail.com> wrote:
>> > Dear Pwscf,
>> >
>> > In my phonon calculations i got one imaginary mode in gamma to X
>> direction.
>> > I want to know which mode it is? and due to which atom it is happening?
>> >
>> > I checked the case.ph.out file. In this file it is given like below.
>> >
>> > Mode symmetry, O_h (m-3m)  point group:
>> >   omega(  1 -  3) =        -16.6  [cm-1]   --> T_1u G_15  G_4- I
>> >   omega(  4 -  6) =        122.3  [cm-1]   --> T_1u G_15  G_4- I
>> >   omega(  7 -  9) =        145.0  [cm-1]   --> T_2g G_25' G_5+ R
>> >   omega( 10 - 12) =        258.5  [cm-1]   --> T_1u G_15  G_4- I
>> >
>> > Here i am attaching the case.agr file
>> >
>> > Here all acoustic modes are given with same frequency. How can know that
>> > particular mode name.
>> >
>> >
>> >  My system is X2YZ type. How can i know this imaginary mode is due to
>> which
>> > atom. I plotted partial phonon density of states also. But all atoms are
>> > giving same contribution in this acoustic mode region.
>> >
>> >  Thank you in advance.
>> >
>> >
>> >
>> > _______________________________________________
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>>
>>
>>
>> --
>> ____________________________________
>> Hui Wang
>> School of physics, Henan University of Science and Technology, Henan,
>> China
>> _______________________________________________
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--
_________________________________________
Filipe Camargo Dalmatti Alves Lima
PhD Student
University of São Paulo, Physics Institute, Materials Physics Department,
Nanomol Group, Brazil.
Phones:    (11) 3091-6881  (USP)
(11) 97408-2755 (Vivo)
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