[QE-users] symmetry traces in sym_band.f90

[Gerson J. Ferreira]

ok. Thanks for this tip! I'll compare the sym_band.f90 and
the sym_band_sub.f90 from thermo_pw and base my code on these.
--
Gerson J. Ferreira
Prof. Dr. @ InFis - UFU
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gjferreira.wordpress.com
Institute of Physics
Federal University of Uberlândia, Brazil
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On Tue, Mar 8, 2022 at 9:20 AM Hongyi Zhao <hongyi.zhao at gmail.com> wrote:

> On Tue, Mar 8, 2022 at 6:08 PM Gerson J. Ferreira
> <gersonjferreira at ufu.br> wrote:
> >
> > Yes, you are right. The first examples I gave above were 2x2 single
> group matrices, but for the numerical case I only had the spinful double
> group ready to show, but I guess it was clear enough for the discussion.
> >
> > Yes, I know what a non-symmorphic symmetry is. My python code calculates
> the matrix representations of generic symmetry operations {S,tau}, where S
> is the point group rotation and tau is a possible fractional translation.
> But it is still under development, we are testing it for different
> materials to make sure it works, and that's why it is not public on github
> yet. We'll make it public once we have a first version and a draft of the
> paper ready.
> >
> > The problem with my python code is that it is too simple. It does the
> calculation using QE plane waves and does not carry the PAW or US
> pseudo-potential corrections. For PAW pseudos we the matrix elements must
> be corrected by the partial-waves, pseudo-partial-waves and projectors,
> while for US pseudos we have to account for the overlap matrix S. I'm not
> account for these, and I have the impression that for symmetry operators
> these corrections are not necessary, since the plane waves should obey the
> symmetry constraints with and without the corrections. But I'm not 100%
> sure yet.
> >
> > In any case, the plan is to drop this python code and implement the same
> thing directly in QE's sym_band.f90 (or a nearly equal new routine). That's
> why I'm currently studying it. If I cannot make it work with sym_band.f90,
> then I'll use my current python code.
> >
> > For this purpose, I need to understand where exactly lies the limitation
> of sym_band.f90 regarding non-symmorphic symmetries. I'm studying the code,
> but if some could give me some hints, I would appreciate it!
>
> I think you should start by studying the following code:
>
> https://github.com/dalcorso/thermo_pw/blob/master/src/sym_band_sub.f90
>
> My point of view is based on the fact that this code is an updated
> version of QE's sym_band.f90 and was developed specifically to solve
> non-symmorphic symmetries, as indicated by the following comment at
> the beginning of it:
>
> !
> ! Copyright (C) 2006-2007 Quantum ESPRESSO group
> ! Copyright (C) 2016-2017 Andrea Dal Corso
> !    (added symmetry analysis at zone border point in nonsymmorphic space
> !     groups)
>
>
> Yours,
> Hongyi
>
>
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