We show that NMR multi-time correlation functions provide interesting new insights into the nature of lithium and silver ion dynamics in solids. For solid ion conductors, they usually probe the elementary jumps of the long-range charge transport. NMR two-time correlation functions yield rates and activation energies of the ionic hopping motion. Moreover, they reveal that the ionic relaxation exhibits a strong nonexponentiality in the studied crystals and glasses. NMR three-time correlation functions enable quantitative determination of the origin of the nonexponentiality. For various solid-state electrolytes, the analysis shows that pronounced dynamical heterogeneities govern the ionic hopping motion. If dynamical heterogeneities exist, NMR four-time correlation functions allow one to measure the time scale of exchange processes within the rate distributions. For silver ion dynamics in a crystalline and a glassy material, the results indicate that initially slow ions exhibit random new rates from broad rate distributions after very few jump events.

The high-temperature partitioning of Fe2+ and Mg between the two nonequivalent octahedral M1 and M2 sites in synthetic olivine (Fa50) was studied by Mössbauer spectroscopy. Powder samples have been equilibrated in annealing experiments performed under reducing oxygen fugacity at temperatures between 500 and 800°C followed by rapid quenching in order to prevent redistribution of cations. M-site ordering with Fe2+ preferring M1, Mg preferring M2 sites increases continuously with rising equilibrium temperature. K D values increase from 1.21 at 500°C to 1.48 at 750°C. The results are consistent with both room temperature as well as in situ high temperature single crystal X-ray diffraction experiments of Heinemann et al. [8, 9].

Recording four-time correlation functions in experiments and computer simulations, we measure the lifetime of dynamical heterogeneities associated with the ionic jump motion in phosphate glasses. 109Ag NMR four-time correlation functions for a silver iodide doped silver phosphate glass indicate that the silver ions exhibit a random new rate from a broad distribution after very few jumps, implying that silver sites featuring fast and slow ionic jumps are intimately mixed rather than grouped into extended domains. Likewise, four-time correlation functions from molecular dynamics simulations of LiPO3 glass show that the dynamical heterogeneities observed for the lithium ionic jumps are short lived. Hence, rapid rate exchange is an important feature of the ion dynamics in an experimental and a model phosphate glass, i.e., the ionic diffusion is comprised of a random series of fast and slow jumps. In addition, we perform simulations for various lattice models to elucidate the interpretation of NMR four-time correlation functions for solid ion conductors, which can differ from that in previous applications of this method.

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Arbeitsbeschaffungsmasnahmen (ABM) waren lange Zeit ein wichtiges Instrument aktiver Arbeitsmarktpolitik (AAMP) in Deutschland. Im Zeitraum 2000 bis 2004 nahmen insgesamt knapp 1 Mio. Personen - teils mehrfach - an diesen Masnahmen teil und es wurden fast 12 Mrd. Euro dafur ausgegeben. Eine umfassende Wirkungsanalyse mit Berucksichtigung von Effektheterogenitaten war bis zur Aufbereitung der prozessproduzierten Daten der Bundesagentur fur Arbeit (BA) fur wissenschaftliche Untersuchungen aufgrund der unzureichenden Datenlage nicht moglich. Die Verwendung der umfangreichen Kundendaten der BA ermoglicht die wissenschaftliche Evaluation der Wirkungen der Programme der aktiven Arbeitsmarktpolitik; ABM sind das erste Instrument, dessen Wirkungen mit Berucksichtigung zielgruppenspezifischer Unterschiede in den Effekten untersucht werden konnten. In der Studie werden die wichtigsten Ergebnisse der Analysen der ABM-Programme zusammengefasst. Dabei werden die Implikationen fur die Arbeitsmarktpolitik auch vor dem Hintergrund der Hartz-Reformen und den damit verbundenen institutionellen Neuerungen diskutiert. (Autorenreferat, IAB-Doku)

The relation between structure and ion dynamics in the three polymorphs of Ag(5)Te(2)Cl has been investigated using (109)Ag, (125)Te, and (35)Cl NMR spectroscopies. Specifically, the influence of the structural phase transitions observed near 240 K (P2(1)/c<-->P2(1)/n) and near 332 K (P2(1)/n<-->I4/mcm) upon silver ion mobilities has been studied by temperature dependent (109)Ag NMR lineshapes and spin-lattice relaxation times. While the superionic high temperature phase alpha-Ag(5)Te(2)Cl is characterized by a molten cationic sublattice, fast ion dynamics in the medium-temperature phase beta-Ag(5)Te(2)Cl occurs in spatially restricted regions comprising all the crystallographically distinct silver sites. Temperature dependent magic-angle-spinning linewidths yield an activation energy of 0.38 eV, consistent with 0.44 eV measured from dc electric conductivities. For the low-temperature gamma-modification, results of two- and three-time (109)Ag correlation spectroscopies provide a detailed insight into the nature of the silver ionic hopping motion. Temperature dependent jump rates measured by two-time correlation functions yield an activation energy E(a)= 0.48 eV. (109)Ag NMR three-time correlation functions indicate that the non-exponential relaxation behavior of the silver ions can be attributed to a broad distribution of jump rates rather than correlated forward-backward jumps. Nevertheless, all the silver ions are mobile down to temperatures of about 185 K.

The origin of the non-exponential relaxation of silver ions in the crystalline ion conductor Ag7P3S11 is analyzed by comparing appropriate two-time and three-time 109Ag NMR correlation functions. The non-exponentiality is due to a rate distribution, i.e., dynamic heterogeneities, rather than to an intrinsic non-exponentiality. Thus, the data give no evidence for the relevance of correlated back-and-forth jumps on the timescale of the silver relaxation.

A highly unusual structural evolution has been observed in temperature dependent studies of the fast ion conductor Ag7P3S11, using X-ray diffraction, Raman scattering, 31P and 109Ag NMR spectroscopy, and electrical conductivity measurements. At 205 K the high-temperature γ-phase (space group C2/c) undergoes a phase transition to an intermediate β-phase of different symmetry. At a temperature near 130 K another phase transition is observed resulting in the formation of an ordered low-temperature α-modification crystallizing in the same space group as the γ-phase. Restoration of the high-temperature-phase symmetry in the low-temperature phase is unambiguously confirmed by single-crystal X-ray structure determination and 31P solid state NMR peak multiplicities. The re-entrant phase behavior is further supported by temperature dependent electrical conductivity measurements, which reveal that the activation energies of the dc conductivity for the α- and γ-phases are identical and significantly lower compared to those measured in the β-phase. Although the β- to γ-phase transition is associated with a change in enthalpy, those observables reflecting silver ion dynamics show no discontinuities at the phase transition temperature. The high-temperature γ-phase crystallizes in the monoclinic system, space group C2/c (No. 15), a=23.999(2)Å, b=6.3621(3)Å, c=24.909(2)Å, β=110.926(7)°, R=0.0318 (300 K). The low-temperature α-phase is isostructural with a=24.090(1)Å, b=6.3400(3)Å, c=24.581(1)Å, β=110.870(6)°, R=0.0317 (120 K). Contrary to the situation in γ-Ag7P3S11, all the silver atoms are well-localized in the α-phase.

Various Ag-109 NMR techniques are used to study silver diffusion in silver iodide/silver phosphate glasses. In particular, for the first time, four-dimensional (4D) NMR is applied on solid ion conductors. All experiments consistently show that silver dynamics are governed by a very broad, continuous distribution of correlation times G (lg tau). First, over a wide temperature range, the Ag-109 NMR spectra are well described by a weighted superposition of a rigid-limit spectrum and a motionally narrowed line resulting from the slow and the fast silver ions, respectively. Further, very stretched Ag-109 NMR two-time correlation functions are observed where a lack of correlation for t --> infinity indicates that there are no truly immobile silver ions. When fitting the decays to a Kohlrausch function, exp(-(t /tau)(beta)), the stretching parameter amounts to betaapproximate to0.2 and the mean correlation times [tau] show activation energies consistent with those reported for the dc conductivity. Finally, in 4D Ag-109 NMR echo experiments, the existence of dynamical heterogeneities is proven by the selection of a subensemble of silver ions with a dynamical behavior different from the ensemble average. In addition, the information content of multi-dimensional NMR experiments on solid ion conductors is visualized by model simulations.

By applying one- and two-dimensional 109Ag NMR, we demonstrate that silver diffusion in silver iodide/silver phosphate glasses is governed by a very broad, continuous distribution of correlation times G(lg tau). As a consequence, over a wide temperature range, the 109Ag NMR spectra can be described by a weighted superposition of a Gaussian and a Lorentzian where these line-shape components result from the slow and the fast silver ions in G(lg tau), respectively. For the 109Ag NMR two-time correlation functions F2(t), measured as a stimulated echo, a very stretched decay to F2SS(t(m)) = 0 is observed. When fitting to a Kohlrausch function, exp[-(t/tau)beta], a stretching parameter beta approximately = 0.2 is found. The temperature dependence of the mean correlation time of silver dynamics is described by an Arrhenius law where the activation energy is consistent with the one reported for the dc conductivity sigma(dc). In addition, it is shown that the effect of complex dynamical processes on NMR multi-time correlation functions can easily be calculated when performing random-walk simulations for schematic models such as the random-barrier model and the random-energy model. Based on these models it is possible to simulate various NMR observables and the mean square displacement, thus revealing the information content of multi-dimensional NMR experiments on solid ion conductors.

We demonstrate that one- (1D) and two-dimensional (2D) 109Ag NMR is well suited to study diffusion in crystalline and glassy silver ion conductors. In 1D 109Ag NMR, especially when applying magic angle spinning, the local environments of the silver sites can be characterized. 2D 109Ag NMR allows one to record two-time correlation functions which directly monitor dynamics of single silver ions. These techniques are used to elucidate microscopic properties of polycrystalline Ag7P3S11. In this silver ion conductor, Ag+ motion results in non-exponential correlation functions which decay to a finite plateau value. At all temperatures, the data are well described by a modified Kohlrausch function f(t)=(1−C)exp[−(t/τ)β]+C, where β≈0.42 and and C≈0.12. The temperature dependence of the mean correlation time 〈τ〉 obeys an Arrhenius law with activation energy Ea=0.37 eV. Our results indicate that 109Ag NMR probes elementary silver ion jumps which are the basis of macroscopic ion transport. In addition, we investigate for the first time dynamics in glassy ion conductors by means of 2D NMR. In the glasses (AgI)0.3–(AgPO3)0.7 and (AgI)0.3–(1/3)(Ag4P2O7)0.7 glasses, silver motion manifests itself in correlation functions which decay in an extremely stretched manner, i.e., β=0.21, to C=0. Hence, there is no evidence for domain segregation into silver phosphate glass and AgI clusters, in which case a bimodal rate distribution would be expected.

Chemie Ingenieur TechnikVolume 73, Issue 3 p. 270-274 Wissenschaftliche Kurzmitteilung Messung und Simulation des Inertgaseinflusses auf Explosionsgrenzen bei erhöhten Anfangsdrücken Kai Holtappels Dipl.-Chem., Kai Holtappels Dipl.-Chem. Institut für Technische Chemie, Gerhard-Mercator-Universität Duisburg; z.Z. Bundesanstalt für Materialforschung und -prüfung (BAM), D-12200 BerlinSearch for more papers by this authorChristian Brinkmann Dipl.-Ing., Christian Brinkmann Dipl.-Ing. KRUPP POLYSIUS, Graf-Galen-Straße 17, D-59269 BeckumSearch for more papers by this authorSiegmund Dietlen Dr.-Ing., Siegmund Dietlen Dr.-Ing. Bundesanstalft für Materialforschung und -prüfung, D-12200 BerlinSearch for more papers by this authorVolkmar Schröder Dr., Volkmar Schröder Dr. Bundesanstalft für Materialforschung und -prüfung, D-12200 BerlinSearch for more papers by this authorJohannes Stickling Dr.-Ing., Johannes Stickling Dr.-Ing. Institut für Thermische Verfahrenstechnik, Univ.-GH Paderborn, Warburger Straße 100, D-33095 PaderbornSearch for more papers by this authorAxel Schönbucher Prof. Dr., Axel Schönbucher Prof. Dr. Institut für Technische Chemie, Gerhard-Mercator-Universität Duisburg; Lotharstraße 1, D-47057 DuisburgSearch for more papers by this author Kai Holtappels Dipl.-Chem., Kai Holtappels Dipl.-Chem. Institut für Technische Chemie, Gerhard-Mercator-Universität Duisburg; z.Z. Bundesanstalt für Materialforschung und -prüfung (BAM), D-12200 BerlinSearch for more papers by this authorChristian Brinkmann Dipl.-Ing., Christian Brinkmann Dipl.-Ing. KRUPP POLYSIUS, Graf-Galen-Straße 17, D-59269 BeckumSearch for more papers by this authorSiegmund Dietlen Dr.-Ing., Siegmund Dietlen Dr.-Ing. Bundesanstalft für Materialforschung und -prüfung, D-12200 BerlinSearch for more papers by this authorVolkmar Schröder Dr., Volkmar Schröder Dr. Bundesanstalft für Materialforschung und -prüfung, D-12200 BerlinSearch for more papers by this authorJohannes Stickling Dr.-Ing., Johannes Stickling Dr.-Ing. Institut für Thermische Verfahrenstechnik, Univ.-GH Paderborn, Warburger Straße 100, D-33095 PaderbornSearch for more papers by this authorAxel Schönbucher Prof. Dr., Axel Schönbucher Prof. Dr. Institut für Technische Chemie, Gerhard-Mercator-Universität Duisburg; Lotharstraße 1, D-47057 DuisburgSearch for more papers by this author First published: 09 March 2001 https://doi.org/10.1002/1522-2640(200103)73:3<270::AID-CITE270>3.0.CO;2-VCitations: 10AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat References [1] »CHEMSAFE — Sicherheitstechnische Kenngrößen von brennbaren Stoffen«, Datenbank, entwickelt in einem gemeinsamen Projekt der BAM, PTB und Dechema, Version 1.3.3, 12/99 [2] Stickling J. Thiel-Böhm A. Der Einfluss des Druckes auf die Explosionsgrenzen gasförmiger Gemische; Fortschrittberichte VDI, Reihe 3: Verfahrenstechnik, VDI Verlag, Düsseldorf 305 1993 [3] Stickling J. Einfluss von Inertgasen auf die Explosionsgrenzen organischer Gase und Dämpfe homologer Reihen — Experimentelle Bestimmung und Simulation, Dissertation, Universität-GH Paderborn. 2000 [4] Holtappels K. Untersuchung des Druckeinflusses auf die Explosionsgrenzen der Systeme C2H4/N2/Luft und C2H4/CO2/Luft, Diplomarbeit, Gerhard-Mercator-Universität Duisburg 1998 [5] Zabetakis G. Flammability Characteristics of Combustible Gases and Vapours, Bureau of Mines Bulletin 627, U.S. Government Printing Office, Washington D.C. 1965 [6] Nemeth A. Einfluss des Druckes auf die obere Zündgrenze von Sauerstoffgemischen der Paraffin- und Olefin-KW's mit der Atomzahl C1 — C4; Magyar Kémiai Folóirat. 66 1960 25 30 [7] Brinkmann C. Der Einfluss des Druckes auf die Explosionsgrenzen im System Methan/Inertgas/Luft bei Raumtemperatur, Diplomarbeit, Universität-GH Paderborn 1994 [8] Warnatz J. Maas U. Dibble R. W. Verbrennung — Physikalisch-chemische Grundlagen, Modellierung und Simulation, Experimente, Schadstoffentstehung, 2 Auflage, Springer-Verlag, Berlin 1997 89 91 Citing Literature Volume73, Issue3März 2001Pages 270-274 ReferencesRelatedInformation

ABSTRACT: After unification, East German GNP dropped severely, total employment fell to about two thirds of the former level. Long‐term labour market prospects remain poor. From the very beginning up to now, labour market policy (short‐time work, early retirement schemes, work creation measures, further training and retraining) absorbed much of the surplus labour supply. Regulations were changed to allow for‘“mega‐measures” (contrasting the traditional individual approach). A new co‐financing model links work‐creation measures more closely to regional structural policy. A labour market infrastructure was built up in a short time, including new elements such as‘“employment promotion companies” and‘“reconstruction agents“.