[Wien] Crystal field splitting in empty 3d band of Fe2O3
Dear Y. Ding, For the material Fe2O3 having the formal high-spin Fe3+ and a closed up-spin shell, I think LDA (when giving an insulating solution) or LDA+U partial d-DOS can well show the t2g-eg (if being eigenorbitals) crystal field splitting. Just a note: have you worked with a hexagonal lattice coordinate or a local octahedral coordinate ? May the short Fe-Fe pair or a trigonal field distort too much the crystal field level diagram ? best regards -- H. Wu On Thursday 17 September 2009 07:51, Pavel Novak wrote: Dear Yang Ding, yesterday I forgot third point, which perhaps could give answer to your question. If U is chosen such that it put d-states close to the oxygen p- states, hybridization increases and it shifts the d-levels down if EdEp, or up if EdEp. Regards Pavel On Wed, 16 Sep 2009, Pavel Novak wrote: Dear Yang Ding, care is needed when estimating the crystal field splitting from the LDA+U calculation using the DOS. There are two reasons for it. First, the LDA+U lower the energy of more occupied states and increase the energy of less occupied states. Even if the bands are above Fermi energy, they contain nonzero fraction of electrons (cf :QTL in scf file), which is different for eg and t2g states, hence LDA+U distorts the splitting. Second, the selfinteraction of the d-electrons is present, again distorting the crystal field splitting. Regards Pavel Novak On Tue, 15 Sep 2009, Yang Ding wrote: 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,
[Wien] Crystal field splitting in empty 3d band of Fe2O3
Dear Yang Ding, care is needed when estimating the crystal field splitting from the LDA+U calculation using the DOS. There are two reasons for it. First, the LDA+U lower the energy of more occupied states and increase the energy of less occupied states. Even if the bands are above Fermi energy, they contain nonzero fraction of electrons (cf :QTL in scf file), which is different for eg and t2g states, hence LDA+U distorts the splitting. Second, the selfinteraction of the d-electrons is present, again distorting the crystal field splitting. Regards Pavel Novak On Tue, 15 Sep 2009, Yang Ding wrote: 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, --
[Wien] Crystal field splitting in empty 3d band of Fe2O3
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 -- next part -- An HTML attachment was scrubbed... URL: http://zeus.theochem.tuwien.ac.at/pipermail/wien/attachments/20090915/6bb07f33/attachment.htm
