[Pw_forum] query on e-ph matrix element

[Hua Bao]

Dear QE-users and Paolo,

Thanks for your explanation.
Actually we can completely understand npert(irr).
However, there is still difficulty for us to relate npert(irr) to a
specific \nu.

When we track the quantity "npert", we could not find out where it is
modified (although we know it is defined in phcom.f90).

Would you please point out the relationship between npert and \nu?
Just point out which files we need to look into will be helpful.

Thanks,
Hua


On Mon, Dec 12, 2011 at 5:44 AM, Paolo Giannozzi <giannozz at democritos.it>wrote:

> On Sun, 2011-12-11 at 00:31 -0500, Ajit Vallabhaneni wrote:
>
> > I had gone thru the source code "elphon.f90" for this purpose.
>
> wow! you are a brave man
>
> > I could figure out all the variables like k,i,j,q but not nu.
> > I see a variable 'imode0' which i cannot figure out its purpose.
> > Can someone please help me with identifying the nu ?
>
> the el-ph matrix elements are calculated for each irrep, i.e.
> displacement patterns transforming into each other under the
> symmetry operations of the small group of each wavevector.
> There are nirr irreps, each having dimension npert(irr).
> The code runs over irreps: irr=1,..,nirr, then over irrep
> components: ipert=1,..,npert(irr), and imode0+ipert is the
> index of each displacement pattern. Only when the el-phon
> coefficient "gamma" is calculated are phonon modes (contained
> in matrix "dyn") actually used.
>
> P.
> --
> Paolo Giannozzi, IOM-Democritos and University of Udine, Italy
>
>
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