| Electron delocalization, whether over an entire solid or a local environment of a few atoms, contributes to many macroscopic properties of materials, including conductivity, malleability, ductility, optical properties, and chemical reactivity. Despite its importance, few existing techniques can directly determine the degree of delocalization within a particular bond. In this work, it is hypothesized that, for otherwise similar systems, asymmetry in the pair distribution function (PDF) as determined by extended x-ray absorption fine structure (EXAFS) spectroscopy is correlated to the degree of electron delocalization.; The accuracy of using EXAFS curve-fitting with theoretical standards to determine the asymmetry of the PDF is first established by finding thermal expansion, harmonic Debye-Waller factor, and EXAFS third cumulant for two FCC metals, nickel and copper. The results yield a temperature dependence that agrees well with theory, although the third cumulant shows an offset that indicates that absolute values determined by this method are not reliable. Fortunately, only relative values, which appear to be quite accurate, are necessary for exploring the hypothesis presented.; The technique is then used to find the bond responsible for the semiconductor-metal transition of titanium sesquioxide, to establish the presence of charge-transfer in solid iodine, and to rank the relative amount of stabilizing charge available to the carbon-bromine bond of butyl bromide isomers. In the latter case, the role of hyperconjugation and the inductive effect is discussed. In all cases, the EXAFS third cumulant is found to increase with increasing electron delocalization for systems that are otherwise similar.; General considerations of EXAFS analysis are also discussed, including background subtraction, constraint schemes for multiple-scattering paths, the effects of the finite and discrete Fourier transforms used, and the effects of sample inhomogeneity. |
