Dear Wien2k mailing list, recently I've become interested in calculating XPS shifts for some TiO2- based compounds. For some initial testing I've took plain rutile and anatase, made a supercells around 100 atoms and calculated shifts of core O 1s state to get familiar with the process. I've tried two approaches: deltaSCF and the Slater's transition state as suggested for example here: http://www.mail-archive.com/wien%40zeus.theochem.tuwien.ac.at/msg01128.html . The Slater's transition state approach seems to work fine and the rutile O 1 s state is predicted 0.38eV deeper than in the anatase, in accordance with experimental value (0.4eV ), however for deltaSCF approach I get completely different trend and the rutile O 1s state is predicted 1eV above anatase O 1s. Since in all papers and tutorials I've read the both approaches should give very similar results, it is quite bothering me, why I'm getting this difference. Can anyone suggest a reason for this discrepancy? The cases were converged with respect to number of k-points as well as Rkm and the supercell size should also hopefully be enough... I've also tried LDA vs PBE, however the result were the same. Any ideas?
Best regards Pavel Ondračka  Pfeifer, V., Erhart, P., Li, S., Rachut, K., Morasch, J., Brötz, J., … Klein, A. (2013). Energy Band Alignment between Anatase and Rutile TiO 2. The Journal of Physical Chemistry Letters, 4(23), 4182–4187. http://doi.org/ 10.1021/jz402165b
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