[Wannier] h(r) hoppings in AO basis

[David Vanderbilt]

Ganesh,

Regarding this part

> Does anyone know if it is possible to transform the current
> h(r) matrix elements, which is in the WF-basis, to (say
> an atom centered) atomic-orbital basis within wannier90?
> The transformation might be lossy (i.e. it might be a projection)
> depending on the system of course, but would be good to compare
> with other TB-fitting codes which use such atomic-orbital basis
> to represent the Hamiltonian.

To do this, we normally choose trial functions that have the
desired chemical symmetry, and then do zero iterations of the
maxloc procedure.  That is, we use the WFs that are obtained
just by projection on the trial functions.  We also include
unoccupied bands if needed to "complete the shell" of WFs on
each atom.  Because we skip the iterative localization, these
may not be quite as localized as the MLWFs, but they may be
good for your purposes.

David

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