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Drickamer, H.G. Christoe, Charles William 2011-07-13T15:51:22Z 2011-07-13T15:51:22Z 10000-01-01 1969 Using the inter-atomic distance as a parameter, Mossbauer spectra have been observed for the three isomorphic ferric compounds K3FeF6, Na3 FeF6 and (NH4)3FeF6' In addition, the compressibility and the pressure dependence of cia were determined by X-ray diffraction for the ferrous compound FeF2 , In all of these compounds, the local environment of the iron ion is a slightly distorted octahedron of fluoride ions. A detailed analysis was made of the quadrupole pplitting of the Mossbauer spectra for both the ferrous and the ferric salts. The analysis proceeded along two lines: the usual pointcharge approximation and a covalent approximation based upon configuration interaction. Although the quadrupole splitting increased with pressure in the ferric case--whereas it decreased in the ferrous case--the local crystalline distortions were shown to decrease in both cases when the pressure exceeded about fifty kilobars. The covalent contribution was shown to be a significant portion of the total field gradient at the iron sites for the ferric compounds; that is, it is of the same order of magnitude as the gradient produced by the distorted octahedron. For the ferrous compound, the covalent contribution was shown to be negligible compared to the gradient produced by the ferrous valence electron, although it did tend to diminish the latter effect. Both the point-charge and the covalent models predict zero quadrupole splitting in the event of a truly regular octahedral (or tetrahedral) iron environment. Submitted by Carolyn Mead (cmead2@illinois.edu) on 2011-07-13T15:51:22Z No. of bitstreams: 1 1969_christoe.pdf: 3135166 bytes, checksum: 88c17a7c0dc3d17235aa4f63cf13b084 (MD5) Made available in DSpace on 2011-07-13T15:51:22Z (GMT). No. of bitstreams: 1 1969_christoe.pdf: 3135166 bytes, checksum: 88c17a7c0dc3d17235aa4f63cf13b084 (MD5) Previous issue date: 1969 Restriction data tranferred 2014-07-01T11:32:49-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: Thesis Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Carolyn Mead (cmead2@illinois.edu) on 2011-07-13T15:51:22Z Item is restricted indefinitely. Thesis U of I Only 6074149 http://hdl.handle.net/2142/25794 en 1969 Charles William Christoe quadrupole interaction iron-fluoride compounds inter-atomic distance Mossbauer spectra compressibility x-ray diffraction The effect of high pressure on the quadrupole interaction in iron-fluorine compounds Dissertation / Thesis text Physics Physics University of Illinois at Urbana-Champaign Dissertation Ph.D.