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[matthieu verstraete <matthieu.jean.verstraete@gmail.com>]

You have forgotten a factor of 1/M in the definition of the dynamical
matrix. See the book by Born and Huang, for instance, or eq 11 of

PHYSICAL REVIEW B                                VOLUME 55, NUMBER 16
                                        15 APRIL 1997-II
             Dynamical matrices, Born effective charges, dielectric
permittivity tensors,
            and interatomic force constants from density-functional
perturbation theory
                                                        Xavier Gonze
Changyol Lee

226 = sqrt(mass(Si)) in atomic units of mass.

Matthieu

On Tue, Jun 16, 2009 at 11:14 AM, <or_pong@hotmail.com> wrote:
>    In order to test my comprehension, eigen value problem of dynamical 
> matrix
> (from ABINIT output) had been solved using both Octave and Mathcad 14. My
> octave command had been shown.
>    [U,e]= eig(Dyn);
>    eival = sqrt(e);
> Where Dyn is dynamical matrix.
>
> Octave eigen values  of silicon crystal at q = 0 0 0 are
>    0, 0, 0, 0.282, 0.282, 0.282.
>
>  Phonon energies in Hartree :
>   0.000000E+00  0.000000E+00  0.000000E+00  2.345206E-03  2.345206E-03
> 2.35E-03
>
>    Octave results had been compared with Phonon energies in Hartree (same
> ABINIT output) value by value. From the comparisions, I can write a relation
> between any couple.
>    eival_octave / phonon energy = 226.26
>
> Please give me any suggestion about unit of Octave results.
>
> Thank you very much,
>



-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Dr. Matthieu Verstraete

European Theoretical Spectroscopy Facility (ETSF)
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