Dien Li

Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Al, Si, P and S K- and L-edge X-ray absorption near-edge structure (XANES) spectra of a large selection of metal sulfide and silicate minerals and some glasses have been studied using monochromatized synchrotron radiation.;S K- and L-edge XANES spectra of metal sulfides are qualitatively interpreted based on MO/energy band models, reveal the DOS of unoccupied S s-, p- and d-like states, provide new insight into the electronic structure of the conduction band, and demonstrate the bonding interaction of metal d electrons with S 3s and 3p electrons. The S K- and L-edges shift to high energy with increase in oxidation state of sulfur from sulfides to sulfur, sulfite and sulfates, and also with increase in energy gap and decrease in reflectivity of metal sulfides.;Si K- and L-edge and Al K-edge XANES of silica polymorphs, silicate and aluminosilicate minerals are interpreted based on the qualitative MO calculation of MO{dollar}\sb4{dollar} and MO{dollar}\sb6{dollar} (M = Si{dollar}\sp{lcub}4+{rcub}{dollar} and Al{dollar}\sp{lcub}3+{rcub}){dollar} clusters, multiple scattering effects, and comparison with the spectra of model gas phase molecules. Four- and six-coordinated Si and Al in minerals can Se unambiguously distinguished based on the chemical shift of the edge features. The chemical shifts of the Si K- and L-edges and Al K-edge also correlate with the polymerization of the MO, clusters, substitution of Al for Si, M-O bond distance, bond valence, distortion of the polyhedra and cation compositions of the second coordination shell. Al K-edge spectra can now be used to determine the distribution of Al between tetrahedral and octahedral sites in minerals and glasses.;Precious opals are shown to contain structural units of amorphous and crystalline cristobalite, the proportions of which can be estimated semi-quantitatively, using the Si K- and L-edge spectra. Si and P K- and L-edge XANES spectra of SiO{dollar}\sb2{dollar}-P{dollar}\rm\sb2O\sb5{dollar} and Na{dollar}\sb2{dollar}O-SiO{dollar}\sb2{dollar}-P{dollar}\rm\sb2O\sb5{dollar} glass systems with P{dollar}\rm\sb2O\sb5\leq30{dollar} mol% show that Na{dollar}\sb2{dollar}O depolymerizes silicate melts, PO{dollar}\sbsp{lcub}4{rcub}{lcub}3-{rcub}{dollar} copolymerizes the silicate melts; and the speciation of P in these systems are monophosphate, pyrophosphate and metaphosphates with different chain length, depending on the content of P{dollar}\rm\sb2O\sb5.{dollar}



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