[Wien] Crystal field splitting in empty 3d band of Fe2O3

[Yang Ding]

Dear WIEN2k  users,

I am really new to WIEN2k, and wondering if you could give your advice 
and experience on following question concerning the crystal filed 
splitting calculated from WIEN2k.

In order to understand if the pre-edge splitting appearing in the Fe 
K-edge  spectra (1s-4p transition) measured by emission-XANES on Fe2O3 
[Groot et al. J. Phys.: Condens. Matter 21 (2009) 104207 
<http://www.iop.org/EJ/abstract/0953-8984/21/10/104207/>], is linked to 
crystal-filed splitting in 3d empty band. We did a very preliminary 
ground state calculation using WIEN2k based on GGA+U (and LSDA+U) with U 
= 4 eV structure to check the crystal field splitting in empty d band 
above Fermi level.

As a result, we found that above 2-6 eV above Fermi level, the energy of 
t2g is higher than that of eg. This result is similar to what reported 
by Rollsman et al (PHYSICAL REVIEW B 69, 165107 (2004) 
<http://prola.aps.org/abstract/PRB/v69/i16/e165107>) on Fe2O3. In his 
calculation (GGA/LSDA+U , U= 4eV), the energy of t2g is also higher than 
that of eg. So my question is why the t2g and eg are reversed in DFT, 
but the Multiplet calculation gives contradictory results (i.e from 
Groot et al.).

I noticed that  Glatzel et al (PHYSICAL REVIEW B 77, 115133 (2008) 
<http://prola.aps.org/abstract/PRB/v69/i16/e165107>) reported that they 
obtained the "right" crystal field splitting using (LDA+U, U=6 eV) from 
WIEN2k.   So we wonder if we might missed something in the calculations?

Thanks  in advance for your help,
-- 

Yang Ding 
<http://www.aps.anl.gov/Users/Scientific_Interest_Groups/HPSynC/people/%7EYDing.html>

Staff Scientist

RM-B3180/Blgd-401

HPSynC at Advanced Photon Source

Argonne National Laboratory

9700 S. Cass Avenue

Argonne, IL 60439

Phone: 630-252-6288

Email: yangding at aps.anl.gov

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