The ABINIT Users Mailing List ( CLOSED )

[Xavier Gonze <gonze@pcpm.ucl.ac.be>]

Dear Sebastien,

sebastien.hamel@umontreal.ca wrote:
>  I was wondering if anaddb could handle the calculation of the phonon spectrum
>  of a molecule with a partly optimized/partly contrained geometry.
>
>  How should it react to an uncomplete DDB?
>
>  From what I can see,aznaddb returns 0 for every values if the DDB is used as 
> is.

Yes, this is the present way of treating incomplete information.
The rationale was the following : an incomplete DDB is usually
useless, except if the provided information just spans one or more 
representations
of the symmetry group for phonons (i.e., if the phonons spanned by the
treated perturbations decouple from the other phonons). This often happens
with rather symmetrical solids. If the missing information is set to zero,
then, the only non-zero frequencies corresponds to the "treated" phonons.
(I hope this is not too diffocult to understand).

Do you think you can make something else with an incomplete DDB ??

Good continuation,
Xavier