[Wannier] Spin Down Channel Trapped in Local Minimum

[Patrick Taylor]

Dear Wannier-ists,

I am currently attempting to wannierise a set of isolated valence bands for a spin-polarised system. I have successfully obtained MLWFs for the spin-up channel - these have very low Re/Im ratios and interpolate the band structure very well - but I cannot replicate this for the spin-down channel. For the spin-up channel, I used the SCDM method for initial projections, and ran wannier90 to reach a convergence threshold of 1.0e-10 on the spread functional. Applying the same procedure to the spin-down channel yields MLWFs which are almost as well localised (the total spread is marginally higher) but the Re/Im ratio is very large, suggesting that I am getting stuck in a local minimum.

What I have tried so far:

  *   SCDM + random noise during minimisation
  *   Starting from projections on appropriately-chosen atomic orbitals
  *   Starting from totally random projections

In each case, I end up with more or less the same total spread and the same large Re/Im ratios.

Perhaps my intuition is incorrect, but this is all the wrong way round in my head. The spin-up channel contains d-bands at similar energy to p-bands, and yet this wannierises very well. The spin-down channel contains only the p-bands (the d-bands are above the Fermi level), and yet I cannot seem to escape the local minimum.

Any advice as to how I could further troubleshoot this issue would be much appreciated (and forgive my ignorance if I am missing obvious steps - I am relatively new to the world of Wannier functions).

Thanks,

Patrick

Patrick J. Taylor
Doctoral Researcher
Morgan Group

1S 1.15,
Department of Chemistry,
University of Bath,
BA2 7AY
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