[Wannier] Defining projections for a system

[Mostofi, Arash]

Dear Ghadiyali,

Our experience is that when computing Wannier functions for an isolated set of bands, setting the projections to “random” usually works just fine - in other words the minimisation is fairly robust to the initial guess for the WFs.

When computing WFs for entangled bands, this is less true and it is usually important to provide both a set of projection centres that correspond to your chemical intuition for where the final WFs might be, and to adjust the frozen/inner and outer energy windows appropriately to include the states that are needed in the final subspace. At the moment this needs some trial and error and experience, but we intend to work actively in the very near future on improving and automating this aspect.

Best wishes,

Arash


—
Arash Mostofi — www.mostofigroup.org<http://www.mostofigroup.org>
Director, Thomas Young Centre @Imperial
Imperial College London



On 31 Mar 2017, at 10:19, Mohammed Ghadiyali <m786g at live.co.uk<mailto:m786g at live.co.uk>> wrote:

Hi All,

I 'm trying to learn, how to use Wannier90 interface with Quantum ESPRESSO. The tutorial provided is great
but I 'm not able to understand as how to define the projections for a given system. Is there any general guide
lines or rules to follow. What as of now I understood is that the projections help to converge the system, but
that it self is a question of how?

Regards,
Ghadiyali Mohammed Kader,
University of Mumbai.
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