[Ifeffit] Lost second shell

Frenkel, Anatoly frenkel at bnl.gov
Mon Feb 2 20:14:17 CST 2009

Nice plots, and good data too, with a low amount of noize. It is indeed a very sad looking Er-O contribution and almost nothing else except for a small bump near 3 A where Zn-Zn appears in ZnO. For Er-O, the peak position is shifted to the right relative to a nominal Zn-O position in ZnO (at around 1.5 A, not correcting for the phase shift), as expected due to the larger size of Er ions compared to Zn.
Thus, because of that bump at 3 A it is not really a clear cut situation where you can tell confidently that Er does not substitute for Zn. However, in ZnO, the Zn-Zn peak is higher in intensity than Zn-O, while here it is much much lower. Thus, if Er does substitute for Zn, the entire Er-O cage must be displaced from a high symmetry position relative to Zn atoms in order to produce large disorder in Er-Zn pair lengths that causes reduction of Er-Zn single scattering contribution to EXAFS and, in turn, explains the small bump at 3A. It would also help you if you found the coordination number of Er-O pairs and compared it with that of Zn-O in ZnO. 


From: ifeffit-bounces at millenia.cars.aps.anl.gov on behalf of Eugenio Otal
Sent: Mon 2/2/2009 8:34 PM
To: ifeffit at millenia.cars.aps.anl.gov
Subject: [Ifeffit] Lost second shell

Here I attach some pictures.
I also have luminescence measurements an found a great disorder but I could not find changes in the cell parameters by XRD refinements. I perfored XANES simulations for ZnO sustituted by Er and the spectra is really different. I cannot believe that the Er is in Zn site, but maybe the structure changes and the simulation is not so "real".


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