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The journal of physical chemistry / C 127(8), 4021 - 4032 (2023). doi:10.1021/acs.jpcc.2c07650, The state of the surface near-region during CO hydrogenation of Ni(111) and Ni(211) single crystal surfaces was investigated using various gas mixtures between 150 and 500 mbar, 200 and 325 °C, by operando X-ray photoelectron spectroscopy. We report how higher temperatures and hydrogen content correlate with a movement of CO away from the on-top configurations and toward multicoordinated sites of the nickel surface and how a nickel carbide is formed in the surface near region, particularly at high partial pressures of CO and lower temperatures. The presence of the carbide affects the CO bonding and was observed to be reduced during hydrogen-rich conditions and temperatures above 250 °C., Published by Soc., Washington, DC

ACS applied nano materials 6(9), 8004 - 8016 (2023). doi:10.1021/acsanm.3c01306, We investigated Cu nanoparticles (NPs) on vicinal and basal ZnO supports to obtain anatomistic picture of the catalyst’s structure under in situ oxidizing and reducing conditions.The Cu/ZnO model catalysts were investigated at elevated gas pressures by highenergy grazing incidence X-ray diffraction and ambient pressure X-ray photoelectronspectroscopy (AP-XPS). We find that the Cu nanoparticles are fully oxidized to Cu$_2$Ounder atmospheric conditions at room temperature. As the nanoparticles swell duringoxidation, they maintain their epitaxy on basal ZnO (000±1) surfaces, whereas on thevicinal ZnO (10$\bar{14}$) surface, the nanoparticles undergo a coherent tilt. We find thatthe oxidation process is fully reversible under H$_2$ flow at 500 K, resulting in predominantlywell-aligned nanoparticles on the basal surfaces, whereas the orientation of CuNPs on vicinal ZnO was only partially restored. The analysis of the substrate crystaltruncation rods evidences the stability of basal ZnO surfaces under all gas conditions.No Cu-Zn bulk alloy formation is observed. Under CO$_2$ flow, no diffraction signalfrom the nanoparticles is detected, pointing to their completely disordered state. TheAP-XPS results are in line with the formation of CuO. Scanning electron microscopyimages show that massive mass transport has set in, leading to the formation of largeragglomerates., Published by ACS Publications, Washington, DC

The electronic excitation occurring on adsorbates at ultrafast time scales from optical lasers that initiate surface chemical reactions is still an open question. Here, we report the ultrafast temporal evolution of X-ray absorption spectroscopy (XAS) and X-ray emission spectroscopy (XES) of a simple well known adsorbate prototype system, namely carbon (C) atoms adsorbed on a nickel (Ni(100)) surface, following intense laser optical pumping at 400 nm. We observe ultrafast (~100 fs) changes in both XAS and XES showing clear signatures of the formation of a hot electron-hole pair distribution on the adsorbate. This is followed by slower changes on a few ps time scale, shown to be consistent with thermalization of the complete C/Ni system. Density functional theory spectrum simulations support this interpretation., 33 pages, 12 figures. Submitted to Physical Review Letters

Performing fundamental operando catalysis studies under realistic conditions is a key to further develop and increase the efficiency of industrial catalysts. Operando X-ray photoelectron spectroscopy (XPS) experiments have been limited to pressures, and the relevance for industrial applications has been questioned. Herein, we report on the CO oxidation experiment on Pd(100) performed at a total pressure of 1 bar using XPS. We investigate the light-off regime and the surface chemical composition at the atomistic level in the highly active phase. Furthermore, the observed gas-phase photoemission peaks of CO$_2$, CO, and O$_2$ indicate that the kinetics of the reaction during the light-off regime can be followed operando, and by studying the reaction rate of the reaction, the activation energy is calculated. The reaction was preceded by an in situ oxidation study in 7% O$_2$ in He and a total pressure of 70 mbar to confirm the surface sensitivity and assignment of the oxygen-induced photoemission peaks. However, oxygen-induced photoemission peaks were not observed during the reaction studies, but instead, a metallic Pd phase is present in the highly active regime under the conditions applied. The novel XPS setup utilizes hard X-rays to enable high-pressure studies, combined with a grazing incident angle to increase the surface sensitivity of the measurement. Our findings demonstrate the possibilities of achieving chemical information of the catalyst, operando, on an atomistic level, under industrially relevant conditions.

We investigated Cu/ZnO model catalysts for methanol synthesis to obtain an atomistic picture of activation and deactivation processes under in situ oxidizing and reducing conditions. We have investigated Cu nanoparticles with different shapes and aspect ratios grown epitaxially on basal and vicinal ZnO surfaces at elevated gas pressures by high energy grazing incidence X-ray diffraction and ambient pressure X-ray photoelectron spectroscopy (AP-XPS). We find that the Cu nanoparticles are fully oxidized to Cu2O under atmospheric conditions at room temperature. During oxidation, they maintain their epitaxy on basal ZnO (000-1) surfaces, whereas on the vicinal ZnO (10-14) surface, the nanoparticles undergo a coherent tilt. We find that the oxidation process is fully reversible under H2 flow at 500 K, resulting in predominantly well-aligned nanoparticles on the basal surfaces, whereas a random orientation is preferred for the (10-14) surface. Under CO2 flow, no diffraction signal from the nanoparticles is detected, pointing to their completely disordered state. The AP-XPS results are in line with the formation of CuO. The analysis of the substrate crystal truncation rods evidences the stability of basal ZnO surfaces under all gas conditions. No proof for Cu-Zn alloy formation is found. Scanning electron microscopy images show that massive mass transport has set in, leading to the formation of larger agglomerates, which is detrimental to the catalyst’s performance.

The active chemical state of zinc (Zn) in a zinc-copper (Zn-Cu) catalyst during carbon dioxide/carbon monoxide (CO 2 /CO) hydrogenation has been debated to be Zn oxide (ZnO) nanoparticles, metallic Zn, or a Zn-Cu surface alloy. We used x-ray photoelectron spectroscopy at 180 to 500 millibar to probe the nature of Zn and reaction intermediates during CO 2 /CO hydrogenation over Zn/ZnO/Cu(211), where the temperature is sufficiently high for the reaction to rapidly turn over, thus creating an almost adsorbate-free surface. Tuning of the grazing incidence angle makes it possible to achieve either surface or bulk sensitivity. Hydrogenation of CO 2 gives preference to ZnO in the form of clusters or nanoparticles, whereas in pure CO a surface Zn-Cu alloy becomes more prominent. The results reveal a specific role of CO in the formation of the Zn-Cu surface alloy as an active phase that facilitates efficient CO 2 methanol synthesis.

ACS catalysis 12, 7609 - 7621 (2022). doi:10.1021/acscatal.2c00905, Carbide formation on iron-based catalysts is an integral and, arguably, the most important part of the Fischer–Tropsch synthesis process, converting CO and H2 into synthetic fuels and numerous valuable chemicals. Here, we report an in situ surface-sensitive study of the effect of pressure, temperature, time, and gas feed composition on the growth dynamics of two distinct iron–carbon phases with the octahedral and trigonal prismatic coordination of carbon sites on an Fe(110) single crystal acting as a model catalyst. Using a combination of state-of-the-art X-ray photoelectron spectroscopy at an unprecedentedly high pressure, high-energy surface X-ray diffraction, mass spectrometry, and theoretical calculations, we reveal the details of iron surface carburization and product formation under semirealistic conditions. We provide a detailed insight into the state of the catalyst’s surface in relation to the reaction., Published by ACS, Washington, DC

Journal of the American Chemical Society 144(16), 7038 - 7042 (2022). doi:10.1021/jacs.2c00300, The CO hydrogenation reaction over the Rh(111) and (211) surfaces has been investigated operando by X-ray photoelectron spectroscopy at a pressure of 150 mbar. Observations of the resting state of the catalyst give mechanistic insight into the selectivity of Rh for generating ethanol from CO hydrogenation. This study shows that the Rh(111) surface does not dissociate all CO molecules before hydrogenation of the O and C atoms, which allows methoxy and other both oxygenated and hydrogenated species to be visible in the photoelectron spectra., Published by American Chemical Society, Washington, DC

Angewandte Chemie 134(3), e202111021 (2022). doi:10.1002/ange.202111021, Subsurface oxygen has been proposed to be crucial in oxide-derived copper (OD-Cu) electrocatalysts for enhancing the binding of CO intermediates during CO$_2$ reduction reaction (CO$_2$RR). However, the presence of such oxygen species under reductive conditions still remains debated. In this work, the existence of subsurface oxygen is validated by grazing incident hard X-ray photoelectron spectroscopy, where OD-Cu was prepared by reduction of Cu oxide with H$_2$ without exposing to air. The results suggest two types of subsurface oxygen embedded between the fully reduced metallic surface and the Cu$_2$O buried beneath: (i) oxygen staying at lattice defects and/or vacancies in the surface-most region and (ii) interstitial oxygen intercalated in metal structure. This study adds convincing support to the presence of subsurface oxygen in OD-Cu, which previously has been suggested to play an important role to mitigate the σ-repulsion of Cu for CO intermediates in CO$_2$RR., Published by Wiley-VCH, Weinheim

The journal of chemical physics 157(16), 164705 (2022). doi:10.1063/5.0114399, We report on carbon monoxide desorption and oxidation induced by 400 nm femtosecond laser excitation on the O/Ru(0001) surface probed by time-resolved x-ray absorption spectroscopy (TR-XAS) at the carbon K-edge. The experiments were performed under constant background pressures of CO (6 × 10$^{−8}$ Torr) and O$_2$ (3 × 10$^{−8}$ Torr). Under these conditions, we detect two transient CO species with narrow 2$π^*$ peaks, suggesting little 2π* interaction with the surface. Based on polarization measurements, we find that these two species have opposing orientations: (1) CO favoring a more perpendicular orientation and (2) CO favoring a more parallel orientation with respect to the surface. We also directly detect gas-phase CO2 using a mass spectrometer and observe weak signatures of bent adsorbed CO2 at slightly higher x-ray energies than the 2$π^*$ region. These results are compared to previously reported TR-XAS results at the O K-edge, where the CO background pressure was three times lower (2 × 10$^{−8}$ Torr) while maintaining the same O$_2$ pressure. At the lower CO pressure, in the CO 2$π^*$ region, we observed adsorbed CO and a distribution of OC–O bond lengths close to the CO oxidation transition state, with little indication of gas-like CO. The shift toward “gas-like” CO species may be explained by the higher CO exposure, which blocks O adsorption, decreasing O coverage and increasing CO coverage. These effects decrease the CO desorption barrier through dipole–dipole interaction while simultaneously increasing the CO oxidation barrier., Published by American Institute of Physics, Melville, NY

Nature Communications 12(1), 6117 (2021). doi:10.1038/s41467-021-26372-y, Heterogeneous catalyst surfaces are dynamic entities that respond rapidly to changes in theirlocal gas environment, and the dynamics of the response is a decisive factor for the catalysts���action and activity. Few probes are able to map catalyst structure and local gas environmentsimultaneously under reaction conditions at the timescales of the dynamic changes. Here weuse the CO oxidation reaction and a Pd(100) model catalyst to demonstrate how suchstudies can be performed by time-resolved ambient pressure photoelectron spectroscopy.Central elements of the method are cyclic gas pulsing and software-based event-averaging byimage recognition of spectral features. A keyfinding is that at 3.2 mbar total pressure ametallic, predominantly CO-covered metallic surface turns highly active for a few secondsonce the O2:CO ratio becomes high enough to lift the CO poisoning effect before masstransport limitations triggers formation of a���5 oxide., Published by Nature Publishing Group UK, [London]

International audience; Hard X-ray photoelectron spectroscopy (HAXPES) is a powerful technique to observe chemical and electronic states of atoms buried inside materials. Recently, a laboratory-based HAXPES system with high throughput has been developed, combining a high-flux Ga (Kα＝9.25 keV) X-ray source and a high-transmission photoelectron analyser. In this article, research using the HAXPES Lab is reviewed, and the data are compared with those using synchrotron light sources. The HAXPES Lab is an attractive option not only for scientists but also for industrialists needing rapid answers for research and development.

Applied spectroscopy 75(2), 137 - 144 (2021). doi:10.1177/0003702820942798, We present a new method to maintain constant gas pressure over a sample during in situ measurements. The example shown here is a differentially pumped high-pressure X-ray photoelectron spectroscopy system, but this technique could be applied to many in situ instruments. By using the pressure of the differential stage as a feedback source to change the sample position, a new level of consistency has been achieved. Depending on the absolute value of the sample-to-aperture distance, this technique allows one to maintain the distance within several hundred nanometers, which is below the limit of typical optical microscopy systems. We show that this method is well suited to compensate for thermal drift. Thus, X-ray photoelectron spectroscopy data can be acquired continuously while the sample is heated and maintaining constant pressure over the sample. By implementing a precise manipulator feedback system, pressure variations of less than 5% were reached while the temperature was varied by 400 ℃. The system is also shown to be highly stable under significant changes in gas flow. After changing the flow by a factor of two, the pressure returned to the set value within 60 s., Published by Sage, London

The application of photoelectron spectroscopy using hard X-rays (HAXPES) is becoming increasingly popular as a powerful spectroscopic tool in materials science. The success of HAXPES lies in the fa...

13th International Conference on Synchrotron Radiation Instrumentation, SRI2018, Taipei, Taiwan; AIP conference proceedings 2054(1), 040010 (2019). doi:10.1063/1.5084611, A new undulator beamline (P22) for hard X-ray photoelectron spectroscopy (HAXPES) was built at PETRA III (DESY, Hamburg) to meet the increasing demand for HAXPES-based techniques. It provides four special instruments for high-resolution studies of the electronic and chemical structure of functional nano-materials and catalytic interfaces, with a focus on measurements under operando and/or ambient conditions: (i) a versatile solid-state spectroscopy setup with optional wide-angle lens and in-situ electrical characterization, (ii) a HAXPEEM instrument for sub-µm spectro-microscopy applications, (iii) an ambient pressure system (> 1 bar) for operando studies of catalytic reactions and (iv) a time-of-flight spectrometer as a full-field k-microscope for measurements of the 4D spectral function ρ(EB,k). The X-ray optics were designed to deliver high brightness photon flux within the HAXPES energy range 2.4 – 15 keV. An LN$_2$-cooled double-crystal monochromator with interchangeable pairs of Si(111) and (311) crystals is optionally combined with a double channel-cut post-monochromator to generate X-rays with variable energy bandpass adapted to the needs of the experiment. Additionally, the beam polarization can be varied using a diamond phase plate integrated into the beamline. Adaptive beam focusing is realized by Be compound refractive lenses and/or horizontally deflecting mirrors down to a spot size of ∼20x17 µm$^2$ with a flux of up to 1.1x10$^{13}$ ph/s (for Si(111) at 6 keV)., Published by AIP Publ., Melville, NY

X-ray micro computed tomography (μCT) is used for the morphological characterization of three-dimensional (3D) embroidered current collectors for LiFePO 4 batteries. A conventional 2D planar configuration (aluminium foil as current collector) and two types of 3D embroidered configurations were compared. The μCT images were used to identify the different components in each configuration as well as to evaluate the corresponding volume fractions, porosities, mass fractions and apparent densities. Microtomographic scans complement analysis of typical galvanostatic charge/discharge cycles and confirm the suitability of 3D embroidered current collectors for their use in lithium-ion batteries.

Review of scientific instruments 90(10), 103102 - (2019). doi:10.1063/1.5109321, We present a new high-pressure x-ray photoelectron spectroscopy system dedicated to probing catalytic reactions under realistic conditions at pressures of multiple bars. The instrument builds around the novel concept of a “virtual cell” in which a gas flow onto the sample surface creates a localized high-pressure pillow. This allows the instrument to be operated with a low pressure of a few millibar in the main chamber, while simultaneously a local pressure exceeding 1 bar can be supplied at the sample surface. Synchrotron based hard x-ray excitation is used to increase the electron mean free path in the gas region between sample and analyzer while grazing incidence, Published by American Institute of Physics, [S.l.]

Synthesis and Crystal Structure of Na10[M3O6][MO3] (M = Fe, Mn) with a Remark on the Magnetic Properties Single crystals of Na10[M3O6][MO3] (M = Mn, Fe) may be obtained via a redox reaction of CdO with the respective transition metal in the presence of Na2O and a flux as red single crystals, which are sensitive to moisture. The crystal structure (determined from IPDS data, , Z = 6) contains isolated trigonal aplanar [MO3] units and layers of [MO4] tetrahedra connected via corners to three-membered rings, which share common edges resulting in the formation of twelve-membered rings. The statistical occupancy of 21 out of 60 sodium atoms per unit cell is discussed and calculations of the Madelung Part of the Lattice Energy (MAPLE) are given. Furthermore, we report on the magnetic properties of Na10[Mn3O6][MnO3] in close relation to the structural entities.

Na 11 [CuO 4 ][SO 4 ] 3 was obtained from a redox reaction of CuO with Na 2 O 2 in the presence of Na 2 O and Na 2 SO 4 in sealed Ag containers under Ar atmosphere at 600°C. The crystal structure has been determined from X-ray single crystal data at 293 and 170 K ( Pnma , Z =4). The lattice parameters have been refined from X-ray powder data at 293 K as well: a =1597.06(6) pm, b =703.26(3) pm, c =1481.95(6) pm. The structure contains isolated distorted square-planar [CuO 4 ] 5− anions and non-coordinating sulfate groups. Furthermore, we report calculations of the Madelung Part of the Lattice Energy (MAPLE) and some of the physical properties of Na 11 [CuO 4 ][SO 4 ] 3 .

Na26Mn39O55 wurde durch eine Redoxreaktion von metallischem Mangan mit CdO in Gegenwart von Na2O und Na2SO4 als Mineralisator in Form roter Einkristalle mit oktaedrischem Habitus erhalten. Die Kristallstruktur konnte anhand von Einkristalldaten bestimmt werden (Fd3¯m, Z = 8, a = 2377, 4(3) pm bei 293 K und a = 2372, 5(2) pm bei 130 K). Das seltene charakteristische Strukturelement eines T5-Supertetraeders, [Mn35O56], zeichnet die Kristallstruktur des neuen gemischtvalenten Natrium-Oxomanganats(II, III), Na26Mn39O55, aus. Uber erste Untersuchungen des ungewohnlichen magnetischen Verhaltens wird berichtet. The First T5-Supertetrahedron in Oxide Chemistry: Na26Mn39O55 Na26Mn39O55 has been obtained from a redox reaction between manganese metal, CdO in the presence of Na2O and Na2SO4 as a flux component as red single crystals with octahedral shape. The crystal structure has been determined from single crystal data (Fd3¯m, Z = 8, a = 2377.4(3) pm at 293 K and a = 2372.5(2) pm at 130 K). The rare characteristic structural feature of a T5-Supertetrahedron, [Mn35O56], is observed for this new mixed-valent sodium-oxomanganat(II, III), Na26Mn39O55. First investigations of the magnetic properties are reported.

Results of acoustic emission tests on cylindrical specimens under compression are reported. Deformation-rate-controlled tests with strain rates ranging from 1.1 × 10-6 s-1 to 2.6 × 10-3 s-1 at temperatures between T = -11.2°Cand T = -1.7°C were performed. The investigated snow was fine-grained, with a density varying between 220 and 380 kgm-3. The acoustic emission was measured with two distinct piezoelectric sensors: a wide-band sensor (frequency 100–1000 kHz) and a resonant sensor (frequency 35–100 kHz). The relationship between the applied strain rate and the measured maximum acoustic-emission rate as a function of temperature and density was found to obey a power law, which is valid for the ductile behaviour range. The quantitative and qualitative effects produced on the acoustic emissions during the transition from ductile to brittle behaviour, occurring at strain rates of approximately 1 × 10-3 s-1, are reported. Finally, the influence of the load history on the acoustic emissions of snow is discussed on the basis of a cyclic test, including deformation-controlled loading steps and relaxation steps, performed at different strain rates and different relaxation times.

Na5[CuO2][CO3], Na5[CuO2][SO3], Na5[CuO2][S], and Na5[CuO2][SO4] were obtained as single crystals and powders from reactions of Na2O, Cu2O, and Na2X with X = CO32—, SO32—, S2—, and SO42—, respectively. A redox reaction between CdO and Co metal occurs in the presence of Na2O and Na2X, yielding Na5[CoO2][X] with X = CO32— and S2—. From a mixture of Na2SO4, CdO and Na2O in Ni-containers we observed the formation of Na5[NiO2][S] single crystals. Single crystals of Na25[CuO2]5[SO4]4[S] can be grown by annealing Na5[CuO2][SO3] at 600 °C, leading to the decomposition of SO32—, yielding SO42— and S2— at 550 °C. The structures have been determined from single crystal data and powder data. All structures contain the isolated complex [MO2]3— in a dumb-bell like arrangement. The main feature of these compounds is that the anions SO42—, SO32—, CO32— and S2— are not connected to the transition metal. The formation of Na5[CuO2][X] (X = S2—, SO42—, SO32—, CO32—) has been studied by thermal analysis and in situ X-ray diffraction techniques. Infrared spectra confirm the presence of SO42—, SO32—, and CO32—, respectively, in the structures. Reaktivitat, Synthesen und Kristallstrukturen von Na5[MO2][X] mit M = Co+, Ni+, Cu+; X = CO32—, SO42—, SO32—, S2— und Na25[CuO2]5[SO4]4[S] Na5[CuO2][CO3], Na5[CuO2][SO3], Na5[CuO2][S] und Na5[CuO2][SO4] konnten durch Reaktion von Na2O und Cu2O mit Na2X (X = CO32—, SO32—, S2— bzw. SO42—) einkristallin und als Pulverproben hergestellt werden. Einkristalle und Pulver von Na5[CoO2][X] entstehen bei der Redoxreaktion von CdO und Co-Metall in Gegenwart von Na2O und Na2CO3 bzw. Na2S. Na5[NiO2][S] konnte bei der Umsetzung von CdO, Na2O und Na2SO4 in Ni-Containern in Form von Einkristallen erhalten werden. Einkristalle von Na25[CuO2]5[SO4]4[S] entstehen beim Tempern von Na5[CuO2][SO3] bei 600 °C durch Disproportionierung des Sulfits bei ca. 550 °C zu S2— und SO42—. Die Strukturen konnten anhand von Einkristalldaten bestimmt bzw. durch Pulverdaten belegt werden. Alle Verbindungen enthalten isolierte Komplexe, [MO2]3—, mit der linearen Anordnung einer Hantel. Das charakteristische Merkmal dieser Strukturen ist, das die Anionen SO42—, SO32—, CO32— und S2— nicht an das Ubergangsmetallkation koordinieren. Die Bildung von Na5[CuO2][X] (X = S2—, SO42—, SO32—, CO32—) wurde mittels in-situ-Rontgendiffraktometrie und thermischer Analyse untersucht. Schwingungsspektroskopische Daten bestatigen das Vorliegen von SO42—, SO32— bzw. CO32— in diesen Verbindungen.

Na5[CuO2](OH)2 has been obtained as orange single crystals from mixtures of NaOH, Na2O and Cu2O in sealed Ag containers. The crystal structure has been refined from X-ray diffraction data (IPDS data, Pnma, Z = 4, a = 607.4(1) pm, b = 891.2(1) pm, c = 1201.0(2) pm, R1 = 0.03). The characteristic unit is the bent [CuO2]3– complex (∠(O–Cu–O) = 170°). The reactivity of Na5[CuO2](OH)2 has been studied by DSC and in situ X-ray diffraction techniques. IR spectroscopy has been used for further characterization. The Madelung Part of the Lattice Energy (MAPLE) has been calculated as well. Darstellung, Kristallstruktur und Reaktivitat von Na5[CuO2](OH)2 Na5[CuO2](OH)2 wurde aus Gemengen von NaOH, Na2O und Cu2O in verschlossenen Ag-Containern in Form oranger Einkristalle erhalten. Die Kristallstruktur wurde anhand von Einkristalldaten bestimmt (IPDS-Daten, Pnma, Z = 4, a = 607,4(1) pm, b = 891,2(1) pm, c = 1201,0(2) pm, R1 = 0,03). Die charakteristische Baueinheit, [CuO2]3–, liegt nicht linear vor (∠(O–Cu–O) = 170°). Die Reaktivitat von Na5[CuO2](OH)2 wurde thermoanalytisch (DSC) und mit in-situ-Rontgendiffraktometrie untersucht. Anhand von IR-Spektren erfolgte die weitergehende Charakterisierung. Der Madelunganteil der Gitterenergie, MAPLE, fur Na5[CuO2](OH)2 wird ebenfalls diskutiert.

Die neuen Cyclosilicate konnten durch Umsetzung der binaren Oxide bei 450–500 °C unter Schutzgasatmosphare erhalten werden. Cs5AgSi3O9 kristallisiert in der Raumgruppe P21/m mit den Gitterkonstanten a = 968,2(2) pm, b = 652,7(1) pm, c = 1162,6(3) pm, β = 93,84(2)° und Cs6Na6Si6O18 in R-3m mit a = 1208,0(1) pm, c = 1458,9(2) pm (IPDS-Datensatze). Als strukturbestimmende Merkmale liegen isolierte Ringe, [Si3O9]6– bzw. [Si6O18]12–, vor. In Cs5AgSi3O9 werden diese uber Ag+ zu Ketten verknupft. Schichten aus [NaO4]-Tetraedern separieren die Sechserringe in Cs6Na6Si6O18. In diesen alkalireichen Cyclosilicaten werden unterschiedliche Koordinationen fur Caesium beobachtet (C.N. 3 bis C.N. 9). Daruber hinaus wird uber die MAPLE-Berechnungen beider Cyclosilicate, sowie uber das UV- bzw. IR-Spektrum von Cs5AgSi3O9 berichtet. Praparativ und mit thermoanalytischen Methoden wurde die Reaktivitat von Cs5AgSi3O9 gegenuber metallischem Nickel und Cobalt untersucht. New Alkali Cyclosilicates: Cs5AgSi3O9 and Cs6Na6Si6O18 The new cyclosilicates were obtained from reactions of the binary oxides at 450–500 °C under inert gas atmosphere. Cs5AgSi3O9 crystallizes in the space group P21/m with the lattice constants a = 968,2(2) pm, b = 652,7(1) pm, c = 1162,6(3) pm, β = 93,84(2)° and Cs6Na6Si6O18 in R-3m with a = 1208,0(1) pm, c = 1458,9(2) pm (IPDS data sets). The characteristic features are isolated rings, [Si3O9]6– and [Si6O18]12–, respectively. In Cs5AgSi3O9 these are connected via Ag+ to chains. Layers of [NaO4]-tetrahedra separate the hexameric rings in Cs6Na6Si6O18. Coordination numbers of caesium are observed between C.N. 3 and C.N. 9 in these alkali rich cyclosilicates. MAPLE calculations of both cyclosilicates as well as the absorption and IR spectrum of Cs5AgSi3O9 are presented. Preparative and thermoanalytical techniques have been used to investigate the reactivity of Cs5AgSi3O9 in the presence of cobalt and nickel metal.

Introduction: Pharmacases.de is a novel e-learning website of clinical pharmacology that presents clinically relevant aspects of pharmacology and toxicology in an interactive and multi-medial manner. The objective of the project Pharmacases.de was to develop an innovative concept for creating high quality[for full text, please go to the a.m. URL], Jahrestagung der Gesellschaft für Medizinische Ausbildung (GMA)

Das Lehrbuch (3. bis 4. Semester) erklaert die Begriffe, die das Verhalten von Boeden beschreiben, erlaeutert sie mit einfachen Formeln und Prinzipskizzen und vertieft mit den zum Teil komplizierten Beispielen und der wissenschaftlichen Diskussion der Randbedingungen. Behandelt werden totale und effektive Spannungen, die Spannungsausbreitung im Boden, Formaenderungs- und Festigkeitseigenschaften und der Einfluss von Grundwasser. Grundbauliche Konzepte werden entsprechend den Setzungsberechnungen und Sicherheitsueberlegungen diskutiert. Speziell werden vertikale Baugrubenabschluesse verschiedener Wandsysteme, Sohldruckverteilung unter Fundamenten und Tiefgruendungen behandelt. Neben den allgemeinen Formeln werden in allen Faellen die Auswirkungen geaenderter Randbedingungen beschrieben. In den gerechneten Beispielen werden die benutzten Bodenkennwerte und die berechneten Endergebnisse mitgeteilt. Fuer haeufig vorkommende Bodenarten werden uebliche Bodenkennwerte angefuehrt. Sicherheitsueberlegungen werden fuer einzelne Probleme wie Gleitsicherheit einer Boeschung, Ueberschreiten der Tragfaehigkeit des Bodens, Groesse des Erddrucks, statischer Grundbruch, Groesse der Setzungen, hydraulische Stabilitaet von Baugruben und Auftrieb von Bauwerken angestellt. Vertieft werden die Probleme wie Einfluss des Wassers bei einfach abgestuetzten Waenden, Einfluss der Vorbelastung auf den Spannungsverlauf, Stabilitaetsberechnungen nach Janbu unter Beruecksichtigung von stroemendem Wasser, vertikaler und horizontaler Kraft aus Ankern, Pfaehlen und Auflasten, Einfluss von Auflasten und Kohaesion auf den Erddruck. Tropische Boeden werden als stark veraenderliche Boeden gesondert besprochen und die zusaetzlichen Bedingungen an die Untersuchungen zum Beispiel ueber Schwell- und Quellverhalten definiert. Neu sind die Beschreibung, das mechanische Verhalten und die Beurteilung von Fels (Druckfestigkeit, Trennflaechen) und die Zusammensetzung der Rechenbeispiele aus allen Kapiteln.

In situ X-ray absorption near edge structure (XANES) investigations were carried out at chlorine K edge and palladium L 3 edge to study the mechanism of the thermal decomposition of ammonium hexachloropalladate. The spectra show a characteristic feature for the initial step that might be explained as the formation of the precursor via ligand exchange (Cl ⇒ NH3). Multiple scattering calculations (Feff 8) for the Cl K, Pd and Rh L 3 edges were successful in simulating the XANES spectra of the precursor as well as the reference compounds (NH4)2[PdCl4] and (NH4)3[RhCl6].

Wird ein Korper aus elastischem Material dreidimensional durch die Druckspannungen σ x , σ y und σ z beansprucht (Bild 5.1), so erleidet er Deformationen von

In Abschnitt 1.6 wurde der Durchlassigkeitskoeffizient k, kurz k-Wert genannt, definiert. Er ist ein Mass fur den Widerstand, den das stromende Wasser im Boden erfahrt. Um den vollstandigen hydraulischen Zustand eines durchstromten Bodenprofils zu erfassen, mussen in jedem Punkt das Potenzial H sowie die k-Werte in allen Richtungen bekannt sein. Ist diese Voraussetzung erfullt, so lassen sich alle Fragen nach Druckverhaltnissen in beliebigen Punkten oder nach durchstromenden Wassermengen durch die Losung der Differenzialgleichung der Grundwasserstromung beantworten, z. B. durch die Konstruktion eines Stromungsnetzes. Da die oben erwahnte Bedingung oft nicht erfullbar ist, werden in der Praxis haufig vereinfachte Annahmen herangezogen, wobei sich Extremalannahmen oftmals als hilfreich erweisen.