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In the field of high throughput experimentation (HTE) related to materials sciences and catalysis a large number of test methods and analytical tools have been developed in the last years. As a consequence of the increasing parallelization and integration of the reactor and analysis systems, the requirements for the synthesis methodologies are rising extremely: smallest amounts of material samples of, i.e. different multi component mixed oxides in the μg- or gram-range have to be synthesized reproducibly and fully automated. In order to meet these challenges, the combination of different expert skills in the fields of inorganic synthesis, robotics, automation and related fields are of major importance. Real combinatorial chemistry, meaning the combinatorial permutation of element combinations or synthesis parameters involving statistical synthetic approaches leading to true combinatorial libraries of new functional materials supported by computer aided designs, was not presented yet in scientific community of inorganic solid state chemistry. We present here for the first time a tool for synthetic chemistry, originally developed with the application focus on molecular libraries, to produce inorganic solid state materials. With the so-called Split&Pool (S&P)-principle, it is possible to produce highly diverse materials libraries in the range of 10 3 –10 8 samples with a very simple workflow. Characterization with μ-XRF, optical microscopy and other analysis tools prove the potential of the presented synthesis technique. A powerful enhancement of this synthesis tool is our recently presented “single bead reactor” (SBR), allowing efficient testing of the libraries created by the Split&Pool methodology.

Based on a small number of early experimental results, it can be anticipated that high throughput experimentation (HTE) will play a significant role in the discovery of new zeolites and related materials. The four prime stages in the HTE approach are introduced, in the specific context of work on zeolite synthesis. Key experimental and computational issues are detailed and illustrated by recent literature results. Bottlenecks to achieving the throughput estimated as necessary for a planned level of productivity in new materials discovery are discussed.

The magnetic moments of neutral Sc, V, and Ti atoms supported on a benzene molecule are found to be substantially enhanced over their free-atom value while those of neutral Mn, Fe, and Co atoms experience a similar reduction. The magnetic moment of the neutral Cr atom, the highest (6 μ B ) in the 3d-transition metal series, remains unchanged and that of neutral Ni is completely quenched. These results, based on density functional theory and the generalized gradient approximation, are shown to be a simple consequence of the Pauli exclusion principle. Similar calculations on positively and negatively charged 3d-metal–benzene complexes are carried out.

Crystallographic symmetry plays an important role in structure determination from diffraction or scattering data, in spectroscopy and in simulations. It is convenient and insightful to integrate the display and use of such symmetry data with data analysis and modeling methods. We outline the integration of a suite of crystallographic algorithms, closely coupled with interactive graphical displays. These include techniques for identifying the unit cell of a solid, for automatically determining space and point group symmetries, for generalized displays of symmetry elements overlaid on structural models, and for construction, editing, and transformation of models subject to symmetry constraints. In addition, electron densities derived from periodic density functional calculations can be symmetrized and displayed with the corresponding symmetry elements. Applications of these various capabilities in crystallographic research are illustrated by topical examples.

Some of the areas in which we anticipate, over the next five years, notable advances in the application of molecular simulation to problems in heterogeneous catalysis are considered, in the context of recent progress to date. The areas specifically addressed are: • expanding access to methods, • quantitative structure-property relationships, • building structural models to focus or pre-screen experiments, • confidence in predicting local and extended structure • reaction mechanisms, barriers and kinetics, and • data for chemical process simulations. In each of these areas, we indicate why we consider the topic significant, provide reference to topical work and suggest opportunities for future developments.

A new grid-based algorithm developed at Molecular Simulations, and molecular dynamics method have been applied to modeling the locations of non-framework species in zeolites. This new method locates the energy minima for various frameworks and populates these sites with the non-framework species. The cation locations were predicted in dehydrated zeolite adsorbents and catalysts, such as Na88X, Ca48X, mixed cation zeolite 3A (K60Na36A), and Cu-mordenite (Si/Al=5.0) using only well-known framework structure models. Furthermore, the locations of benzene molecules in a supercage of zeolite Ca48X were correctly predicted via the application of the Monte Carlo docking and molecular dynamics methods. These examples demonstrate that when the framework type is known, the new technique can provide a realistic initial structure input for the challenging task of solving crystal structures of zeolites containing non-framework species.

In blazar research the key to answering such questions as ‘What is the origin the emission mechanism of the high energy photons?’ are the time lags between different wavebands. Progress towards measuring these lags has been hampered by the difficulty of obtaining longterm high energy monitoring, but this situation changed with the launch of RXTE. We report on and discuss the results we have obtained from 18 months of monitoring of 3C 279 and 3C 273 by RXTE in conjunction with other wavebands. Highlights include simultaneous flares in the X-ray/γ-ray and X-ray/IR, both new ground breaking results.

We investigate the feasibility of reconstructing the radial intensity profile of extended stellar sources by inverting their microlensed light curves. Using a simple, linear, limb darkening law as an illustration, we show that the intensity profile can be accurately determined, at least over the outer part of the stellar disc, with realistic light curve sampling and photometric errors. The principal requirement is that the impact parameter of the lens be less than or equal to the stellar radius. Thus, the analysis of microlensing events provides a powerful method for testing stellar atmosphere models., 4 pages LaTeX, to appear in New Astronomy Reviews - proceedings of the Oxford Workshop `Gravitational Lensing: Nature's Own Weighing Scales'. Uses elsart.cls. Paper also available at ftp://info.astro.gla.ac.uk/pub/martin/extended.ps

It has already been shown that microlensing can give rise to a non-zero variable polarisation signal. Here we use realistic simulations to demonstrate the additional information that can be gained from polarimetric observations of lensing events., Comment: 4 pages, LaTeX, 2 figures from 6 postscript files. Uses elsart.sty, graphicx.sty and harvard.sty. To appear in New Astronomy Reviews - proceedings of the Oxford Workshop `Gravitational Lensing: Nature's Own Weighing Scales'

We present the anharmonicity and roughening of Cu surfaces derived from the derivatives of the layer spacings and the surface energies with respect to temperature using the embedded-atom molecular dynamics method. The anharmonicity and roughening of the Cu(110) surface started to increase rapidly around 600 K and 1000 K respectively. In addition, we present the dependence of the surface energy on the temperature for the heteroepitaxial Au/Ag(110) system. The slope of the surface energy was found to be less pronounced compared with that of the free Ag(110) surface system.

Molecular dynamics and Gibbs ensemble Monte Carlo simulations have been used to investigate solvation structures in a dilute supercritical solution of two particle types interacting via Lennard-Jones potentials. Spatial correlations evidenced in the solute-solvent radial distribution functions near the critical point are found to depend strongly on the simulation cell size. There are significant differences between the solvent-solvent and solute-solvent radial distribution functions in the liquid and supercritical states. The mechanism of the development of a dynamic solvation structure around the solute is revealed in the density fluctuations in the critical region. In the liquid state thermal motion prevents strong pair correlations from appearing, masking underlying differences in the solvent-solvent and solute-solvent interaction potentials.

First principles, density functional theory embodied in the DMol program has been applied to agostic ethyl-Ti-complexes, including the dmpe complex, [Ti(-CH 2 CH 3 )C1 3 (dmpe)], where dmpe=(Me 2 PCH 2 ) 2 and its model complex, [Ti(−CH 2 CH 3 )Cl 3 (PH 3 ) 2 ]. The ethyl moiety of the complexes can adopt two limiting conformations, staggered and eclipsed. In the model complex, [Ti(−CH 2 CH 3 )C1 3 (PH 3 ) 2 ], both conformers are found to form agostic structures upon geometry optimization subject to Cs symmetry constraint, with the agostic eclipsed structure being the lower in energy. Full geometry optimization of the dmpe complex, [Ti(−CH 2 CH 3 )C1 3 (dmpe)], yields an agostic structure with geometrical features similar to those measured by single crystal X-ray analysis. It is shown that the HOMO orbital contributes substantially to the agostic bonding.

The structural and electronic properties of neutral cube-like MgO clusters comprising of 8, 18, 32, 48 and 64 atoms have been studied using density functional theory. Geometry optimization of all these stoichiometric clusters was done with C 2v symmetry. The binding energy and the nearest-neighbor separation in these clusters show a progressive approach towards their corresponding bulk values. The densities of states indicate an increase in the width of valence bands with increasing cluster size. Total charge density plots show a relatively stronger dependence of magnesium charge density on the coordination number as compared to that of oxygen in the 64-atom cluster.

Pervasive streaking observed in electron diffraction patterns indicates that natural ferrierite from Lovelock, Nevada, frequently contains planar defects. Modeling and diffraction simulations of seven candidate fault structures indicate that the most commonly observed fault involves c 2 a shear on the (040) planes and can occur with a frequency of up to 30% on the (040) planes in an individual crystallite. Also observed are faults involving a c 2 shear on the (400) planes, which occur with a lower frequency of ∼ 5%.

By extending the theoretical treatments of Cowley and Hendricks and Teller, we have shown that the diffracted wave functions from successive slabs in crystals containing planar defects are related by simple recurrence equations. Recurrence equations greatly simplify the simulation of diffraction from coherently faulted crystals. Selected-area electron diffraction patterns for zeolite beta are simulated and compared with experimental data. Results are consistent with previous observations, made by structure imaging and powder X-ray diffraction, that zeolite beta is a highly disordered intergrowth of two unfaulted end-member structures, with a probability of a stacking fault being close to 50%. The quantitative accuracy of the recursion model of electron diffraction is limited by dynamical scattering effects.

The framework structure of a new sodium zinc arsenate, produced by dehydration of the Na 6 (ZnAsO 4 ) 6 ·8 H 2 0 sodalite analog, has been solved by a simulated annealing method. This method utilizes typical tetrahedral-atom bonding schemes with possible space group and unit cell dimensions to randomly generate possible continuous frameworks and their calculated energies. The Rietveld refinement of the Na 6 (ZnAsO 4 ) 6 solution phase was initially performed on room temperature X-ray data and then continued on low-temperature constant wavelength neutron data. This sodium zinc phosphate is a hexagonal polycrystalline material: space group P6 3 (no. 173), with a = b =9.005 (2) A, c = 8.161 (2) A, a = β = 90°, γ = 120°, V = 573.1 A, and Z = 2, with R = 12.35% and R w = 9.76% for 2756 (CW neutron) powder data points. This tridymite structural analog undergoes a room-temperature transformation to the open-framework sodalite structure.

The discovery of long-range antiferromagnetic order in the high- T c related compounds by neutron diffraction techniques has been of importance in unravelling the basic physics of these materials. We discuss here the nature of the magnetic ordering in both the La 2 CuO 4 -based and YBa 2 Cu 3 O 7− y compounds. The magnetic phase diagram and the spin density distributions obtained from experiments is also discussed.

Full profile analyses of the digitized 29Si NMR spectra of a potassium zeolite L and a gallosilicate analog are described. Both spectra can be fitted reasonably based on the assumption that they comprise only a single set of SinAl(Ga); n=0−4 peaks, reflecting that the mean T-O-T angles for the two T-sites (T=tetrahedral species, Si, Al or Ga) are similar.

The structure of dehydrated gallium mazzite, Na 4 Si 14 Ga 4 O 36 - a synthetic zeolite, has been determined by full profile analysis of powder neutron diffraction data collected on the new powder diffractometer of the Missouri University Research Reactor facility. The hexagonal structure, space group P6 3 /mmc, is similar to that previously reported for the natural mineral mazzite. The partitioning of gallium over the two inequivalent tetrahedral sites is found to be random. Framework vacancies are also observed.

The nature of non-stoichiometry in beta alumina is discussed and mechanisms of non-stoichiometric compensation reviewed. Particular attention is given to the modification of non-stoichiometry, notably demonstrated in investigation of hydrogen beta aluminas where more-nearly-stoichiometric materials have been obtained. We survey the properties of both non-stoichiometric and more-nearly-stoichiometric beta aluminas and provide interpretations of the dependence on stoichiometry of conducting plane composition and structure, lattice constants and ionic conductivity.

The occurrence of long- and/or short-range magnetic ordering in La2−zCuO4−y, La2−xSrxCuO4−y and YBa2Cu3O7−x is reviewed and discussed with respect to the occurrence of high Tc superconductivity in these systems.

The crystal structures present in a series of La(Ba 2− y La y )Cu 3 O 7− x samples with y =0.5, 0.375, 0.25, and 0.125 have been investigated by Rietveld refinements of X-ray and neutron powder diffraction data. For y =0.5 and x =-0.20, the structure is tetragonal, P4/mmm, similar to YBa 2 Cu 3 O 6 , but with 60(2)% occupancy of the O1 (and, equivalently, O5) sites. At all compositions barium populates only the Ba site. For y x x >∼0.0, both O and T phases can occur, although there is apparently a significant barrier to converting such O components to more oxygen rich T materials with x y =0.125 (which significantly improves the superconducting behavior) increases slightly the orthorhombic distortion of the O component, but little affects the relative amount of the T component. The tendency towards O and/or T character is apparently determined primarily by the temperature at which the compound is initially formed, possibly as a result of differences in the La/Ba distribution in the Ba planes. A comparison between the structural results and Meissner effect data from these same samples, suggests that optimal bulk high temperature superconductivity in this system is associated with an orthorhombic distortion. The average structural details of these various materials are discussed and compared with those of the YBa 2 Cu 3 O 7− x system.

Single crystal neutron diffraction measurements at room temperature have revealed the structures of two derivatives of ammonium β-alumina which are produced by sequential loss of ammonia on heating. These crystallographic analyses afford insight into the behaviour of the parent compound and the manner in which the ammonium ions are affected as the temperature is raised above ambient. The mechanism by which stoichiometric materials are formed is considered and the results also shed light on the effective ionic size of the ammonium ion in the host structure.

Two vanadyl(IV) monohydrogenphosphate hydrates have been crystallized from aqueous media and their structures determined by single-crystal X-ray diffraction. The first, a tetrahydrate, VO(HPO4) · 4H2O, is triclinic, P 1 , with a = 6.379(2), b = 8.921(2), c = 13.462(3) A, α = 79.95(2), β = 76.33(3), γ = 71.03(3)°. Final residuals of R1 = 0.058 and R2 = 0.065 were obtained using 1250 unique data and 140 parameters. The second was found to be the hemihydrate, VO(HPO4) · 0.5H2O, with orthorhombic symmetry, Pmmn. Complete structure solution and refinement using data from a 2.7 × 105 μm3 crystal gave atomic parameters in close agreement with those recently reported in a parallel study (C. C. Torardi and J. C. Calabrese, Inorg. Chem. 23, 1308, 1984). Final residuals R1 = 0.041 and R2 = 0.042 were obtained on optimizing the 45 structural variables using 458 observed intensities. The structures of these two hydrates and that of the pyrophosphate, (VO)2P2O7, show a close correspondence. The degree of condensation of the vanadyl octahedra and phosphate tetrahedra, and the amount of water of crystallization in these materials are closely coupled and depend on the formation temperature.

The syntheses of each of the three modifications of rhodium sesquioxide are reviewed and their infrared spectra are described. Models of each of these structures were constructed and manipulated using interactive molecular graphics. Their interrelationship is clearly described and used both to explain the similar features observed in their respective infrared spectra and to predict the occurrence of other discrete structures in the Rh 2 O 3 system. Rhodium sesquisulfide, Rh 2 S 3 , is shown to be isostructural with the high pressure modification, II-Rh 2 O 3 .

A simple analysis of the ratios of selected X-ray powder diffraction intensities from anhydrous sodiumlithium zeolite A samples, Na 12− x Li x Si 12 Al 12 O 48 , shows that Li replaces Na in site I for 0 ≤ x ≤ 8. This result is discussed in relation to previously reported 29 Si NMR data and a model is presented for the cation ordering scheme in the anhydrous mixed material with x = 4. Changes in the X-ray pattern with external water vapor pressure are also described.

The crystal structures of the high-temperature modifications of sodium and silver orthophosphates have been determined using powder neutron diffraction (PND) data. II-Na3PO4 adopts the space group Fm3m with a=7.512(3) A at 400°C. The PO3−4 group is centered around the origin, but it shows high orientational disorder. The sodium ions occupy the 1 4 1 4 1 4 and 1 2 1 2 1 2 sites. II-Ag3PO4, at 650°C, is similar with a=7.722(5) A . The structure of I-Ag3PO4 at room temperature ( P 4 3 n , a=6.0095 (6) A ) has been re-examined by single-crystal X-ray diffraction. The derived model, with R=0.019 for 116 independent reflections, is in agreement with the latest work reported in the literature. The structure of I-Ag3PO4 at 375°C, as determined by PND, has a=6.061 (1) A , and displays no gross modifications from that observed at 25°C, although the anisotropic nature of the silver sites is markedly more pronounced at this higher temperature. The cation mobility is discussed in relation to the high-temperatures structures.

The system Na 3(1−x) Al x ▭ 2x PO 4 , where ▭ represents a cation vacancy, has been examined under ambient conditions at the two compositions x =0.025 and x =0.2 by powder neutron diffraction. The presence of Al 3+ ions stabilises the high-temperature face-centred cubic phase of sodium orthophosphate, II-Na 3 PO 4 , with a 0 =7.424(2) A (x=0.025) and a 0 =7.421(2) A (x=0.2) at 25°C. At the lower dopant concentration, the structure corresponds closely to that of II-Na 3 PO 4 . The PO 3- 4 groups are orientationally disordered about the origin with sodium ions occupying the 1 4 1 4 1 4 and 1 2 1 2 1 2 sites in space group Fm3m. For x =0.2, vacancies are found solely at the 1 2 1 2 1 2 position. This is consistent with the interpretation of these phases in terms of a cation-excess anti-fluorite structure. The influence of the structural evolution on the sodium-ion conductivity is discussed and a basis for the formation of low melting-point glasses for x > 0.5 is proposed.

The structure of the dehydrated gallium analog of zeolite L, K 9 Ga 9 Si 27 O 72 has been determined by full profile analysis of powder neutron diffraction data. The gallium partitioning between the two T-sites (T = Tetrahedral species, Si, Al, or Ga) is random. The individual O-T-O angles show small but consistent deviations from the ideal tetrahedral value. The mean T4OT and T6OT angles are nearly identical in both the present and previously studied LTL-framework structures, enabling assignment of the 29 Si nmr spectra. The observed cation configuration is similar to that described previously for the hydrated (Na,K) aluminum zeolite L which, therefore, suggests that little change in cation distribution accompanies dehydration.

A multidetector, medium resolution, quasielastic and inelastic neutron scattering spectrometer has been designed and built at the Intense Pulsed Neutron Source of Argonne National Laboratory. The main objective in the design is to combine a moderate resolution around zero energy transfer with relatively uniform and high resolution at finite energy transfer up to about 1000 wave numbers. By using the principles of time and energy focusing together with pyrolytic graphite monochrometers and small detectors, we achieve a best resolution at the quasielastic peak of 56 μeV at the final energy of Ef = 3.63 meV. The relative energy resolution at finite energy transfer, ΔE/E, is fairly constant varying between 2% and 4%. The spectrometer has three arms which rotate around the sample covering the angular range 20°–155°. Two of the arms have 13 detectors and the third has 9 detectors. The q range at the elastic position varies from 0.4 to 2.6 A−1. The incident neutron intensity on the sample area of 1 cm×10 cm is about 106 neutrons/s. Results of preliminary measurements on n-butane in the plastic phase, on crystallized Kaolinite, and on tetramethylammonium template cations occluded within zeolites are outlined.

This paper discusses me of the phenomenological aspects of electron beam damage of zeolites in the elektron microscope, with empjasis on changes in crystallite morphology and composition, Zeolite L is used as an example material. In agreement with previous observations on zeolites, damage rates are found to be most sensitive to the amount of water present in the structure and to the presence of framework aluminum. The presence of H + and NH 4 + cations can significantly increase damage rates. The data suggest a dominating damage mechanism in which AlOSi connectivities are broken after attack by acidic species. This attack can occur following ionization of water by the elektron beam, or by beam-induced migration of H + and NH 4 + non-framework cations.

The structure of anhydrous stoichiometric deuterium ..beta..-alumina, DAl/sub 11/O/sub 17/, has been determined at 4.2, 298, 573, and 720 K by profile refinement of powder neutron diffraction data. At each temperature the deuterium is found to lie in well-defined threefold sites close to the spacer oxygen, O(5). There is no evidence for delocalization of the deuterium away from O(5) and such a hydroxyl linkage is in accord with the low protonic conductivity observed in related materials. The effect of this unusual mirror-plane arrangement on the remainder of the structure and the variation with temperature of the lattice constants, bond lengths, and angles are discussed.

The structural and conductivity data on silver orthophospate described recently by Deschizeaux-cheuy et al. are considered in the context of earlier work on the same subject. The results of powder neutron (PND) and single crystal X-ray diffraction (SXD) analyses of Ag 3 P0 4 provide a consistent picuture of how the I-Ag 3 P0 4 structure evolves with temperature. A comparison of independent analyses of II-Na 3 P0 4 by PND and SXD demonstrates that solution and refinement of the structures of even highly disordered superionic materials can, in certain cases, be accomplished using powder diffraction data.

The preparation and crystal structure of ammonium beta alumina is reviewed. The thermal decomposition behaviour and the evolution of the conducting plane composition with temperature is described. The progressions from ammonium beta alumina to hydrogen beta alumina, and thence ultimately to α-alumina, are multi-step processes and a combination of infra-red, DTA, TGA and neutron diffraction investigations have led to a broad understanding of the changes occuring.

We have determined the structural phase diagram of the Ba1−xKxBiO3 system for 0≤x≤0.5 and temperatures from 10K to above 400K. At room temperature the undoped compound, BaBiO3, is monoclinic. With increasing x, the monoclinic phase successively transforms to orthorhombic, and then to cubic phases. As the symmetry increases, first the breathing-mode distortion and then the rotation of BiO6 octahedra are eliminated. The superconducting composition, x≥0.37, is cubic at all temperatures.

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