[Pw_forum] Re: How to determine the thickness in surface phonons calculation?

[Nicola Marzari]

Dear Yingli Niu,

I do not have a straightforward answer - it depends also a lot
on what you want the el-ph for, or why.

My inclination would be this - for any given phonon, the
electron-phonon coupling is given by an integration over
the BZ (see e.g. Mauri 1996 PRL, Eq 2). So, you can always
select, one at a time, surface phonons that interest you.

Then, it's less clear what to do. You could e.g. calculate the
max-loc Wannier functions for the system, and then use only the
ones that sit on the surface to construct, via Bloch sums, the
u_nk's (i.e. the periodic part of the Bloch orbitals) that go
in Eq. 2 above. Or you could directly transform the integral
of Eq 2 into a max-loc representation, then keep only stuff
that is on the surface of the slab.

It's not terribly complicate, but if you are a newcomer to
the field, it requires a lot of homework with the codes.

Both Feliciano Giustino and Ivo Souza, in Berkeley,
might be working at related projects.

nicola


英利 牛 wrote:
> Prof Nicola,
>   Thank you! Thank you very much!!!
>   And thanks a lot for Dr.Claudia Bungaro's PhD paper.
>   Now I kown how to insert the bulk constants in to
> the slab.
>   One more question, I want to calculate the el-ph
> interaction of a metal surface next step. If I use a
> normal method in pwscf, I will get interaction between
> all phonons(surface+resonance+bulk) and all
> electrons(surface+resonance+bulk).If I want to analyse
> the el-ph interaction at surface, should I selected
> the surface phonons and surface electrons out? Does it
> means that I should modify the pwscf source files? May
> I specify the phonon mode of some special q point,
> then calculate the lamda(q,v) with the surface
> electrons?
>   Are there any articles about these?
> Thanks
> Best regards
> 
> Yingli Niu


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Prof Nicola Marzari   Department of Materials Science and Engineering
13-5066   MIT   77 Massachusetts Avenue   Cambridge MA 02139-4307 USA
tel 617.4522758 fax 2586534 marzari at mit.edu http://quasiamore.mit.edu