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Question about symmetry in el-ph calculations

From: "张�s" <zhangting1980323@gmail.com>
To: forum@abinit.org
Subject: Question about symmetry in el-ph calculations
Date: Thu, 27 Sep 2007 21:23:34 +0800
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Dear ABINIT users:

I'm performing el-ph matrix element gkq calculations. I wonder must we calculate all the perturbations, or can we just calculate an irreducible set of perturbations, using symmetry operations to generate other gkq, to reduce the calculation demand. I've seen the code of version 4.6.5, in which el-ph matrix element gkq (via perturbations along cell axis) are squared, and it says these squared gkq^2 will behave like phonon dynamical matrix under symmetry operations. So it seems that we can, but in fact when I try to analysis GKK file contain only the irreducible set of perturbations, anaddb will not run correctly,and says gkk element was not found. I got confused about this point. Can we use just an irreducible perturbation set to get all el-ph matrix elements? If so, how to get them? How the el-ph matrix elements gkq(via a single atom's move along cell axis) transform under symmetry operations? Knowing this we can generate other gkqs. If anyone has experience about it, I'll quite appreciate your help.

Regards

                               Zhang Ting
                               Peking Univ.
                               Sep. 27th 2007

Question about symmetry in el-ph calculations, 张�s, 09/27/2007
- Re: [abinit-forum] Question about symmetry in el-ph calculations, Matthieu Verstraete, 09/27/2007