[Pw_forum] phonon dos normalization

Mousumi Upadhyay Kahaly mousumi at jncasr.ac.in
Fri Sep 9 12:42:25 CEST 2005


In order to cancel first order errors in d/dx form,
and to get better results, each atom is once displaced by
+delta and then by -delta. Then Dynamical matrices are
calculated. Hence matrix size= 2 times the total degrees
of freedom, i.e. twice what you expect.


> Dear PW users,
> After several testing, I found that the phonon density
> of state from the PWscf calculations are normalized to
> six times the number of atoms in a unit cell. That is
> twice of the degrees of freedom. I wonder why don't we
> just normalize it to the degrees of freedom or just to
> one?
> I would appreciate it very much if someone could give
> me an explanation.
> W. YU
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