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

[Vahid Askarpour]

Dear Professor Marzari,

I found a way to solve my problem. I first get the Wannier90 code to calculate the coarse grid M_mn matrix elements. Then I use some of the interpolation routines already in EPW to interpolate M_mn unto the Wannier basis and interpolate back unto the fine k-grid in the Bloch basis. This approach has been used by the EPW code for the overlap of el-ph matrix elements and electron and phonon energies.

Best wishes,

Vahid



> On Apr 7, 2017, at 9:43 AM, Vahid Askarpour <vh261281 at dal.ca> wrote:
> 
> 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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>>> Wannier mailing list
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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
>