[Pw_forum] Factor M in electron-phonon coupling matrix element

[Sridhar Sadasivam]

Prof. Giannozzi,

Thanks for your reply. Yes I also think the formula is valid only for
single-atom unit cells.

I checked Ziman's textbook and it looks like there needs to be a summation
over the atoms in the unit cell for a multi-atom cell. Can I assume that QE
(5.0.3) implements the correct formula for multi-atom unit cell although
the formula given in the user guide is only valid for a single atom cell?

Thanks,
Sridhar


On Mon, May 19, 2014 at 1:57 AM, Paolo Giannozzi
<paolo.giannozzi at uniud.it>wrote:

> M should be the nuclear mass, if I remember correctly (these
> formulas are valid for crystals with a single kind of atoms,
> if I remember correctly)
>
> P.
>
> On Sat, 2014-05-17 at 18:02 +0530, Sridhar Sadasivam wrote:
> > Dear QE users and developers,
> >
> >
> > I am writing to ask for a small clarification in the formula that
> > defines the electron-phonon coupling matrix element (Equation 1 in the
> > phonon user guide:
> > http://www.quantum-espresso.org/wp-content/uploads/Doc/ph_user_guide.pdf)
> >
> >
> > What is 'M' in Equation 1? Is it the total mass of the unit cell?
> >
> >
> > Thanks,
> > Sridhar
> > Purdue University
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>
> --
> Paolo Giannozzi, Dept. Chemistry&Physics&Environment,
> Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
> Phone +39-0432-558216, fax +39-0432-558222
>
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