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[Xavier Gonze <xavier.gonze@uclouvain.be>]

Dear Emmanuel,

The eigenmode characterizing a phonon should always be thought as a  
collective pattern of displacements
describing oscillations with time. The phases (or the real and  
imaginary components) are important, as they will describe
the atomic displacements with a form like

a_r  * cos (omega*t)   + a_i * sin (omega*t)

As suggested by Nishimatsu-san, please read a basic textbook about  
phonons (and normal modes of vibrations).

Best regards,
Xavier


On 18 Aug 2009, at 19:54, Emmanuel Arras wrote:

> Thanks for the reference,
> As I understand it, the comlpex phase it is simply the phase  
> associated with the fourrier transform, that is the action of q.r in  
> the primitive cell ( D(k)=D(-k)* ). So I would say it is useless  
> since the information is already known via q and the atomic positions.
>
> As for the absolute amplitude, it seems to be simply a  
> renormalization factor taking into account the number of atoms,  
> their mass and the frequency of the phonon.
>
> Thank you again.
>
>
>
> Takeshi NISHIMATSU a écrit :
> > Emmanuel,
> >
> > You should read a basic textbook on solid state
> > physics and phonon. Par exemple, CHAPTER 3 of
> > "Theoretical Solid State Physics, Vol.1: Perfect
> > Lattices in Equilibrium" by William Jones and
> > Norman H. March.
> >
> >
> > > when I compute phonons, for each mode, the atomique  
> > > displacementvectors' coordinates are given
> > > by complexe numbers (in anaddb.out,since my _PHVEC file is empty  
> > > whatever eivec but
> > > that'sanother problem). I get that the norm of these complexes are  
> > > thecoordinates of the
> > > atomique displacementvectors, but I wonder what is the meaning of  
> > > the complexe phaseassociated.
> > >  :
> > Hint: D(k) and D(-k)
> >
> > Bonne chance,
>
> --
> Emmanuel ARRAS
> L_Sim (Laboratoire de Simulation Atomistique)
> SP2M / INAC
> CEA Grenoble
> tel : 00 33 (0)4 387 86862