EPW Forum

Hello Everyone,

I want to sort out the contribution of optical and acoustical phonons in electron self-energy. So I have a question regarding the sorting of branch modes in Eq. (3) of Computer Physics Communications 209, 116 (2016). When code write linewidth.elself using verbosity=3 then the imode in linewidth.elself are sorted on the basis of acoustical and optical branches or summation at each (n,k) is over increasing phonon energy irrespective of acoustical and optical mode?

Or how does the summation goes on at crossing of phonon bands, imode is sorted on the basis of mode type or increasing energy?

Looking forward for your reply.
Have a nice evening.

Best wishes,
Dinesh

Hello Everyone,

I read another post exactly on the same question and got my answers.

Sorry for bothering you with repeated question.

Best wishes,
Dinesh

Hello Everyone,

I am back to square one in this question. My understanding of this question was based on the following discussion in the forum

http://epwforum.uk/viewtopic.php?f=3&p=1582

From the end of discussion I found that \nu is based on ranking not by actual mode. Then I come across this paper

http://www.pnas.org/content/pnas/112/17/5291.full.pdf

where they also used EPW code and calculated mode resolved scattering time. The paper is almost 2 years older than the discussion.
In the paper, Did they modified the code and this feature is not included in the code yet?
Or iverbosity =3 (mode resolved line widths), imode is the actual optical and acoustical modes and imode keeps the mode characterstic (throughout the BZ) even at the band crossing.

Thank you very much for your reply in advance.

Best wishes,
Dinesh

Dear Dinesh,

I can confirm that imode just follows the mode ranking, without trying to preserve the mode character at branch crossings etc.
I am not sure if in the PNAS you mentioned the code has been modified or not. Looking carefully, in the Methods section they say
"The scattering rates for the individual phonon modes shown in Fig. 1 are computed by restricting the summation in Eq. 1 to a given phonon mode (i.e., a given phonon branch and thus, a given value of ?)", so it doesn't look like the mode character is fully followed either.

Best
Carla

Dear Carla,

Thank you very much for your quick reply. So my final understanding is imode is based on the index of the branch with increasing frequency at every q-point not on the basis of character of branch.

Best wishes,
Dinesh