[Wannier] Interpolation of u_nk unto a generic k-point

[Vahid Askarpour]

Dear Professor Marzari,

I am attempting to implement a routine into EPW for calculating impurity scattering rates.  The routine is outlined in Europhysics Letters, 109, 57006,2015 for silicon and requires the calculation of the the overlap integral u*_k’(r)u_k(r)dr^3 for a dense k-grid, where the u_k is the periodic part of the Bloch state.

The latest version of the Wannier code calculates the M_mn matrix elements for any pair of the k-points on the coarse grid using the nnkpts parameter. However, I need to find M_mn for dense grids around 100x100x100. Such a dense grid is needed for convergence of the impurity scattering rates in Si. That requires running the non self-consistent calculations for such a dense grid, which is expensive.

So I was hoping to use Wannier interpolation to interpolate either the u_k (or the M_mn’s) from a coarse unto a fine grid (this can be done on the fly so there is no need to store all the interpolated u_k’s) inside EPW. I can then output the M_mn for the dense k-grid.

I would appreciate any suggestions you may have for such an implementation.

Thank you,

Vahid

> On Apr 7, 2017, at 4:15 AM, Nicola Marzari <nicola.marzari at epfl.ch> wrote:
> 
> 
> 
> Well, I guess you never (?) need the u_nk, but expectation values
> calculated on them - be it the energy or other quantities. What would
> you need an arbitrary u_nk for?
> 
> 			nicola
> 
> 
> On 06/04/2017 23:41, Vahid Askarpour wrote:
>> Dear Wannier Community,
>> 
>> The geninterp routine interpolates the energies for a generic k-point.
>> Is it possible for Wannier90 to interpolate the u_nk (periodic part of
>> the Bloch states) from a regular coarse grid defined in the non
>> self-consistent calculation unto a generic k-point?
>> 
>> If not, where would be the best place in the code to implement such a
>> calculation?
>> 
>> Thank you,
>> 
>> Vahid
>> 
>> Vahid Askarpour
>> Department of Physics and Atmospheric Science
>> Dalhousie University,
>> Halifax, NS, Canada
>> 
>> 
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> 
> -- 
> ----------------------------------------------------------------------
> Prof Nicola Marzari, Chair of Theory and Simulation of Materials, EPFL
> Director, National Centre for Competence in Research NCCR MARVEL, EPFL
> http://theossrv1.epfl.ch/Main/Contact http://nccr-marvel.ch/en/project