[DFTB-Plus-User] bulk antiferromagnetic Fe2O3 calculation

[Bálint Aradi]

Dear Kanchan,

Periodic metallic systems can be quite tricky to get converged
sometimes. I was able to get your system converged by following changes:

* First, I did a non-spinpolarized calculation, since as you have
reported, that converges without any problems.

* Then, I've taken the net charges from detailed.out and insterted them
into the input with the keyword InitialCharges.

* With those initial charges, your system converges also spin polarized,
provided I change the initial spin polarization. The values you have
provided

>   SpinPolarisation = Colinear {
>     UnpairedElectrons = 4.0
>     InitialSpins = {
>       AtomSpin = {
>         Atoms = 4:5 14:15 24:25
>         SpinPerAtom = +1.0
>       }
>       AtomSpin = {
>         Atoms = 9:10 19:20 29:30
>         SpinPerAtom = -1.0
>       }
>     }
>   }

are somewhat inconsistent, since you ask for 4 unpaired electrons, but
define an initial spin configuration yielding 12 unpaired electrons! If
I comment out the entire InitialSpins block, the calculation converges
with the steps as described above. It also converges, if I  change the
SpinPerAtom setting to +0.333333 and -0.333333 instead of +1.0 and -1.0,
respectively.

  Best regards,

  Bálint

-- 
Dr. Bálint Aradi
Bremen Center for Computational Materials Science, University of Bremen
http://www.bccms.uni-bremen.de/cms/people/b_aradi/


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