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This paper presents a summary of our structural results obtained from X-ray Absorption Spectroscopy, Anomalous Wide Angle X-ray Scattering and Small Angle X-ray scattering for germanium chalcogenide glasses. At first, the local and the medium range order existing in the structure of GeXx ([MATH] and X=S,Se) binary glasses have been determined. Then, the results obtained for (1-y)GeX2 + yAg2X ternary glasses are presented.

ABSTRACTThe in vitro activities of caspofungin and micafungin against 1,038 yeast isolates have been determined. The caspofungin and micafungin MICs were lower for Candida albicans, Candida glabrata, and Candida tropicalisthan for Candida parapsilosis, Candida guilliermondii, and Candida krusei. A clear correlation was seen between the MICs for the two drugs.

X‐ray absorption spectroscopy (XAS) experiments have been performed on 1.0 and 1.6 MZnBr2aqueous solutions under ambient to supercritical conditions. Both the X‐ray absorption near‐edge structure (XANES) and the extended X‐ray absorption fine structure (EXAFS) show striking evolutions, which indicate major structural changes, with a strong reduction in hydration and the increasing formation of ZnBr pairs. A quantitative analysis of the evolution of the Zn environment is presented that supports the existence of a transition from an octahedral to a tetrahedral environment.

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X-ray absorption fine structure (XAFS) measurements for expanded fluid Se at high temperatures and pressures up to 1650°C and 600 bar have been carried out to investigate the change of local structure with volume expansion. The electronic property of fluid Se changes from a semiconducting one to metallic with increasing temperature and pressure. When the volume is further expanded, the fluid becomes non-metallic vapor. XAFS spectra of the non-metallic vapor shows that the vapor rarer than the critical density consists mainly of Se dimers. When the volume contracts exceeding the critical density, the first peak in the radial distribution function is shifted towards larger distance and is increasingly asymmetrical.

X-ray resonant magnetic scattering experiments using linear and circular polarised light have been caried out at the Ni and Fe L2,3absorption edges on magnetically coupled Ag/Ni and Ag/NiFe multilayers. The strong enhancement of the X-ray magnetic resonant scattering, especially at the Fe L edges, allows to evidence a superlattice magnetic peak due to the antiferromagnetic coupling between Ni or NiFe layers. Magnetic reflections represent several % of the intensity of the charge peak. With the magnetic moments aligned between layers, large changes (up to 75%) in the intensity of the chemical modulation peak have been observed upon reversal of the direction of the magnetic field. For the Ag/Ni, multilayer a detailed analysis gives a magnetic scattering amplitude equal to 8 r0per nickel atom.

Extended X-ray absorption fine structure is used to study local order in silicate glasses around sodium and silicon atoms. It is demonstrated that modifying cations like sodium have well-defined short range order that is complementary rather than incidental to the glass forming silicate network.

Bragg diffraction from an Ag/Ni multilayer was used to determine independently both the real and imaginary parts of the anomalous scattering factor (ASF) around the Ni LIIIand LIIedges in the soft‐X‐ray range. Huge resonant variations were observed with reaching 55and decreasing to −63 at the Ni LIIIedge. The independent measurements of and are tested for coherency using the Kramers–Kronig relation. The values are also compared with those derived from X‐ray absorption methods such as total electron yield and fluorescence yield measurements.

EXAFS spectra of three forms of Al-Cu alloys, namely solid solutions, dispersed G.P. zones and the θ' phase, have been obtained using synchrotron radiation. The well-known structure of the θ' phase has been used to check the validity of the theoretical parameters which enter into the analysis. These experiments lead to an understanding of the core effect around the copper atom in solid solution, the chemical composition of the G.P. zone and the correlated local deformation of the surrounding matrix.In the solid solution the average distance between Cu and its Al nearest neighbours is 2.725 ± 0.02 A, compared to 2.86 A for the Al-Al distance in the matrix. G.P. zones are shown to be monolayers with an average 50-50 composition and the spacing between the two (200) planes is measured to be 1.68 A, compared to 2.0225 A for the d200 in the matrix.

The local structure of amorphous cadmium arsenide semiconducting films has been studied by differential anomalous X-ray scattering. Intensity measurements were carried out on two samples, containing 41 and 74 at.% As, in the vicinity of the absorption K edges of both constituents using synchrotron radiation. The computational procedure, similar to that proposed by Warren for an amorphous sample with more than one kind of atom, was applied to obtain the structural parameters from the experimental data. It has been found that atoms in the amorphous CdAs films remain almost tetrahedrally coordinated and that the investigated films are chemically ordered. The structural changes going from cadmium- to arsenic-rich composition have been revealed. The differential anomalous X-ray scattering technique proved to be effective, providing the evidence for the CdCd and AsAs near neighbour correlations in Cd59As41and Cd26As74, respectively. The simulations of the differential radial distribution functions have shown that for the amorphous film containing 41 at.% As the distorted tetrahedral structure, intermediate between the CdAs and Si III type structures, is adequate to account for the experimental data. At 74 at.% As, the atomic arrangement can be described satisfactorily by the structural model based on the tetragonal CdAs2structure. The structural parameters obtained from the present study and those previously derived using the extended X-ray absorption fine structure and conventional large angle X-ray scattering techniques are compared.

X-ray anomalous diffraction in different geometries and X-ray resonant magnetic scattering have been used to investigate Fe"xMn"1"-"x/Ir(001) superlattices. The influence of the alloy stoichiometry on the structural and magnetic properties has been studied and compared with the bulk alloy properties. The structural results are compared with the magnetic results in order to understand the outstanding properties of these systems.

The structural analysis of (1 - y)GeS2· yAg2S ternary glasses has been carried out using X-ray absorption spectroscopy, anomalous wide angle X-ray scattering and small angle X-ray scattering. All the results are consistent among themselves, and a combined analysis has provided straightforward structural conclusions about the homogeneous distribution of the Ag+cations in the glassy matrix. This improved understanding of the local and medium range order has allowed a discussion of the validity of the various structural models suggested to explain the ionic transport process at the atomic level. This process cannot be explained by a phase-separation model but by correlated Ag+jumps promoted by their large variety of sites.

We discuss advantages and limitations of X-ray absorption fine structure (EXAFS), X-ray diffraction and anomalous X-ray diffraction as structural tools for ordered and (chemically and structurally) disordered solids.

X-ray anomalous scattering has been used for the selective characterisation of the structure of each sublattice in Fe/Ir (001) superlattices. The data have been analysed by comparing the simulated and experimental spectra in q-space at various wavelengths near the absorption edges. This approach, applied to symmetric reflection scans, enables a model-independent determination of the perpendicular lattice spacings of the individual layers.

The element and electronic shell specificities of x-ray resonant magnetic scattering have been used to investigate the induced magnetization of the 5d and 4f electronic states of Ce in a [Ce(10Å)/Fe(30Å)]×100 multilayer. We show that the measurement of the magnetic contribution to the intensities diffracted at low angles at the L2and M4edge of the rare-earth allows to investigate the profile of the 5d and 4f magnetic polarisation across the rare-earth layer. The Ce 5dpolarization is found to be oscillating across the Ce layer with a slow decrease from the interfaces with Fe towards the center of the layer. Preliminary results on the Ce 4f polarisation indicate a constant profile.