[Pw_forum] Doubt in eigenvalues

[Nicola Marzari]

Dear Padmaja,

1) does the impurity give rise to isolated impurity levels ? If
so, I presume you should plot band dispersions, and see flat bands.
Then, you could plot the shape of the eigenstates at the Gamma point
(or, if they are flat, indeed anywhere else), and see which ones look 
like the your eg or t2g

2) you could calculate the overlap between your states at gamma
and the atomic d orbitals of you transition metal - this is done
by the code when doing LDA+U calculations, so there should be
an easy way (that I do not know) to print them out.

3) a more complex approach would be doing wannier postprocessing,
to find out which are those impurity bands. note though that the
localization procedure would probably give you random mixes of these
orbitals, and you need an additional diagonalization step to recover the 
eg/t2g. This is explained in a M. Posternak et al Phys Rev B 2002.

Any other suggestions ?

				nicola


Padmaja Patnaik wrote:
> Dear all
> 
> I am doing calculations on wide band gap semiconductor with a transition 
> metal as impurity. Doing the scf calculations, DOS calculations, finding 
> the magnetic moment etc. My problem comes while plotting the energy 
> levels. What I expected that, the eigen values obtained should  indicate 
> the splitting of levels into t2 and e sublevels. As t2 is 3 fold 
> degenerate and e is two fold, so I expected that the eigen value which 
> is repeated three times those corresponds to t2 and that repeated twice 
> is for e. But the results obtained is quite confusing. I observe many 
> sets of eigen values repeated twice and  thrice near the band gap 
> region. I am performing calculations for both the spins. And this is 
> happening for both spins. More than one set eigenvalues are found to be 
> repeated twice and also thrice for the same K-point value. So how to 
> know which one is the correct eigenvalue for t2 and e levels? Am i doing 
> something wrong? I am looking at the dos output file for this plot.
> Can anybody please advise on this.
> Thanks in advance
> 
> Regards
> Padmaja


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Prof Nicola Marzari   Department of Materials Science and Engineering
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