The synchrotron x-ray absorption near edge structures (XANES) technique was used in conjunction with first-principles calculations to characterize Al-doped ZnO films. Standard characterizations revealed that the amount of carrier concentration and mobility depend on the growth conditions, i.e. H 2 ðor O 2 Þ=Ar gas ratio and Al concentration. First-principles calculations showed that Al energetically prefers to substitute on the Zn site, forming a donor Al Zn , over being an interstitial (Al i ). The measured Al K-edge XANES spectra are in good agreement with the simulated spectra of Al Zn , indicating that the majority of Al atoms are substituting for Zn. The reduction in carrier concentration or mobility in some samples can be attributed to the Al Zn -V Zn and 2Al Zn -V Zn complex formations that have similar XANES features. In addition, XANES of some samples showed additional features that are the indication of some -Al 2 O 3 or nAl Zn -O i formation, explaining their poorer conductivity.

A combination of X-ray absorption spectroscopy (XAS) measurements and quantum mechanical/molecular mechanical (QM/MM) molecular dynamics (MD) simulations has been applied to elucidate detailed information on the hydration structures of Ca(2+) and Cl(-). The XAS spectra (extended X-ray absorption fine structure, EXAFS, and X-ray absorption near-edge structure, XANES) measured from aqueous CaCl(2) solution were analyzed and compared to those generated from snapshots of QM/MM MD simulations of Ca(2+) and Cl(-) in water. With regard to this scheme, the simulated QM/MM-EXAFS and QM/MM-XANES spectra, which correspond to the local structure and geometrical arrangement of the hydrated Ca(2+) and Cl(-) at molecular level show good agreement with the experimentally observed EXAFS and XANES spectra. From the analyses of the simulated QM/MM-EXAFS spectra, the hydration numbers for Ca(2+) and Cl(-) were found to be 7.1 +/- 0.7 and 5.1 +/- 1.3, respectively, compared to the corresponding values of 6.9 +/- 0.7 and 6.0 +/- 1.7 derived from the measured EXAFS data. In particular for XANES results, it is found that ensemble averages derived from the QM/MM MD simulations can provide reliable QM/MM-XANES spectra, which are strongly related to the shape of the experimental XANES spectra. Since there is no direct way to convert the measured XANES spectrum into details relating to geometrical arrangement of the hydrated ions, it is demonstrated that such a combined technique of XAS experiments and QM/MM MD simulations is well-suited for the structural verification of aqueous ionic solutions.

NiAl 2 O 4 , CuAl 2 O 4 , and ZnAl 2 O 4 aluminate spinel nanoparticles were synthesized by sol-gel auto combustion method using diethanolamine (DEA) as a fuel. The effects of calcination temperature on structure, crystallinity, morphology, and optical properties of MAl 2 O 4 (M = Ni, Cu, Zn) have been investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), UV-visible diffuse reflectance spectroscopy (UV-DRS), and photoluminescence (PL) spectroscopy. The XRD and FT-IR results confirm the formation of single-phase spinel structure of NiAl 2 O 4 , CuAl 2 O 4 , and ZnAl 2 O 4 at 1200, 1000, and 600 ℃, respectively. The direct band gap of these aluminate spinels, calculated from UV-DRS spectra using the Kubelka-Munk function, is found to increase with calcination temperature. The PL spectra demonstrate that NiAl 2 O 4 gives the highest blue emission intensity, while CuAl 2 O 4 and ZnAl 2 O 4 exhibit a very strong violet emission. During fluorescence process, the ZnAl 2 O 4 emits visible light in only violet and blue regions, while NiAl 2 O 4 and CuAl 2 O 4 emissions extend to the green region. It seems therefore that the transition metal type and intrinsic defects in these aluminate powders are responsible for these phenomena.

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Illustration of Na ion and small hole polaron migration in Kröhnkite based cathode material.

Glass has been used in ornaments and decorations in Thailand for thousands of years, being discovered in several archeological sites and preserved in museums throughout the country. To date only a few of them have been examined by conventional methods for their compositions and colorations. In this work we report for the first time an advanced structural analysis of Thai ancient glass beads using synchrotron X-ray absorption spectroscopy (XAS) and energy-dispersive X-ray (EDX) spectrometry. Four samples of ancient glass beads were selected from four different archeological sites in three southern provinces (Ranong, Krabi and Pang-nga) of Thailand. Archaeological dating indicated that they were made more than 1,300 years ago. A historically known method for obtaining a red color is to add compounds containing transition elements such as gold, copper, and chromium. For our samples, EDX spectrometry data revealed existing fractions of iron, copper, zinc, and chromium in ascending order. Thus, copper was selectively studied by XAS as being potentially responsible for the red color in the glass beads. K-shell X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) of copper were recorded in fluorescence mode using an advanced 13-element germanium detector. Comparisons with XANES spectra of reference compounds identified two major forms of copper, monovalent copper and a metallic cluster, dispersed in the glass matrix. The cluster dimension was approximated on the basis of structural modeling and a theoretical XANES calculation. As a complement, EXAFS spectra were analyzed to determine the first-shell coordination around copper. XAS was proven to be an outstanding, advanced technique that can be applied to study nondestructively archaeological objects to understand their characteristics and how they were produced in ancient times.

Synchrotron x-ray absorption near edge structures (XANES) measurements of In L3 edge is used in conjunction with first principles calculations to characterize rf magnetron sputtered indium oxynitride at different O contents. Good agreement between the measured and the independently calculated spectra are obtained. Calculations show that the XANES spectra of this alloy are sensitive to the coordination numbers of the In atoms, i.e., fourfold for indium nitride-like structures and sixfold for indium oxide-like structures, but not to the substitution of nearest neighbor N by O or vice versa.

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