[Wannier] momentum matrix interpolation for tetragonal structure

[Li, Junwen]

Dear All,

I am trying to study the dielectric function of MaPbI3 perovskites which have cubic and tetragonal phases. For this, I need to do wannier interpolation for electronic structure and momentum matrix elements. I have developed a code to transform the momentum matrix elements between Bloch states to the representation of Wannier basis.

For the cubic structure, I tried 6x6x6 k grid sampling for the Wannierization and did a test on 6x6x6 grid for the dielectric function . I can see the dielectric function calculated from the wannier-interpolated energyies and momentum matrix matches well with the result directly calculated from Bloch states.

But when I moved to the tetragonal structure with a 4x4x4 sampling grid, the dielectric function from Wannier interpolation is 100 magnitude smaller than that from the Bloch states directly.  I found that the interpolated band structure is very good, but the interpolated momentum matrix elements do not decay as expected. I also tried other grids like 4x4x3, 6x6x4, but could not get correct results.

Any advice would be greatly appreciated. Thank you very much!

Regards,

Junwen Li

Center for Nanoscale Science and Technology
National Institute of Standards and Technology
100 Bureau Drive
Gaithersburg, MD USA 20899
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