Pressure Tuning of the Electronic Spectra of Quasi-One-Dimensional Mixed Valence Semiconductors
Stroud, Mary Ann
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https://hdl.handle.net/2142/69793
Description
Title
Pressure Tuning of the Electronic Spectra of Quasi-One-Dimensional Mixed Valence Semiconductors
Author(s)
Stroud, Mary Ann
Issue Date
1988
Doctoral Committee Chair(s)
Drickamer, Harry G.,
Department of Study
Chemical Engineering
Discipline
Chemical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Inorganic
Engineering, Materials Science
Abstract
The effects of high pressure on the electronic spectra of the mixed valence semiconductors, K$\sb4$(Pt$\sb2$(P$\sb2$O$\sb5$H$\sb2)\sb4$X) $\cdot$3H$\sb2$O; X = Cl, Br were investigated to 10.0 GPa. Their electronic spectra consist of transitions seen in the reduced salt, K$\sb4$(Pt$\sb2$(P$\sb2$O$\sb5$H$\sb2)\sb4$) $\cdot$2H$\sb2$O, and the oxidized salt, K$\sb4$(Pt$\sb2$(P$\sb2$O$\sb5$H$\sb2)\sb4$Cl$\sb2$) $\cdot$2H$\sb2$O, modified to some extent, along with an intervalence charge transfer (IVCT) band characteristic of the mixed valence complex itself. The reduced salt and the oxidized salt have also been studied so that direct comparison with the monohalide could be made. For all four complexes, two first order effects controlled the pressure-induced shifts on the energy of the electronic transitions. These effects, which are discussed in terms of simplified molecular orbital diagrams, are pressure-induced changes in the ligand field splitting in the molecule and an increase in the splitting between the bonding and anti-bonding orbitals within a manifold.
In addition, in the mixed valence complexes the IVCT band yielded information about the structural changes that occurred with increasing pressure. In both complexes, the energy of the IVCT band shifted sharply to lower energy as pressure was increased to 4.0 GPa and then leveled off. This result is consistent with a decrease in the Peierls distortion with increasing pressure.
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