[Wannier] guiding centers

[Elias Assmann]

Dear Nicola,
Dear Wannier90 developers,

Thank you for your prompt and informative reply.  I am taking this
off-list for now, but feel free to bring it back to the mailing list, if
you prefer.

I see from the user guide that the guiding centers are disabled by
default.  In your experience, how important is this functionality in
practical calculations?

I have a specific reason for asking about this.  I am involved with the
wien2wannier interface, and right now I'm preparing it for the next
release.  I wonder if I should make the effort to enable use of the
guiding centers.

More flexible initial projections are one of the things I would like to
implement for the next release.  However, I will still force  initial
projections to be centered on atoms, since projections centered at
arbitrary points are a little more involved with an APW basis.

In particular, I am planning to implement rotations of the spherical
part of the projections.  If I may, I would like to use this opportunity
to ask also about the other projection features pw2wannier90 has but
wien2wannier does not, i.e.

(1) projections centered at arbitrary points, and

(2) ‘r=’ and ‘zona=’.

How important is it to support these features, in your opinion?  I will
not implement them for the next release, but maybe we should keep them
in mind for the future.

Since these are only initial guesses, one might suppose that you can get
along fine with ’standard’ atom-centered projections.  But consider a
case like fcc-Cu, which you cite in your review (Fig. 8).  Is it
necessary to allow interstitial initial guesses to get the interstitial
Wannier centers?


      Elias