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

[Paolo Giannozzi]

On Mon, 2014-05-19 at 16:10 +0530, Sridhar Sadasivam wrote:
> 
> 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? 

I hope so. I didn't write the electron-phonon part (just modified 
and adapted it), but last time I checked (years ago) it seemed fine 
to me.

P.

> 
> 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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-- 
 Paolo Giannozzi, Dept. Chemistry&Physics&Environment, 
 Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
 Phone +39-0432-558216, fax +39-0432-558222