The effect of high pressure on the quadrupole interaction in iron-fluorine compounds

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.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics

Year dc:date

2011

Author dc:creator

• Christoe, Charles William

Contributors dc:contributor

• Drickamer, H.G.

• quadrupole interaction
• iron-fluoride compounds
• inter-atomic distance
• Mossbauer spectra
• compressibility
• x-ray diffraction

Statement dc:rights

• 1969 Charles William Christoe

Language dc:language

en

Identifier

6074149

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/25794