The use of Rich and Suter diagrams to explain the electron configurations of transition elements

Rich and Suter diagrams are a very useful tool to explain the electron configurations of all transition elements, and in particular, the s¹ and s0 configurations of the elements Cr, Cu, Nb, Mo, Ru, Rh, Pd, Ag, and Pt. The application of these diagrams to the inner transition elements also explains the electron configurations of lanthanoids and actinoids, except for Ce, Pa, U, Np, and Cm, whose electron configurations are indeed very special because they are a mixture of several configurations.

Organometallic Hydroxides of Transition Elements

Northern Illinois University DeKalb,Institut fu¨r Anorganische Chemie & Southern Methodist University

Exploring thermal and mechanical properties of selected transition elements under extreme conditions: Experiments at high pressures and high temperatures

Transition metals (Ti, Zr, Hf, Mo, W, V, Nb, Ta, Pd, Pt, Cu, Ag, and Au) are essential building units of many materials and have important industrial applications. Therefore, it is important to understand their thermal and physical behavior when they are subjected to extreme conditions of pressure and temperature. This dissertation presents: • An improved experimental technique to use lasers for the measurement of thermal conductivity of materials under conditions of very high pressure (P, up to 50 GPa) and temperature (T up to 2500 K). • An experimental study of the phase relationship and physical properties of selected transition metals, which revealed new and unexpected physical effects of thermal conductivity in Zr, and Hf under high P-T. • New phase diagrams created for Hf, Ti and Zr from experimental data. • P-T dependence of the lattice parameters in α-hafnium. Contrary to prior reports, the α-ω phase transition in hafnium has a negative dT/dP slope. • New data on thermodynamic and physical properties of several transition metals and their respective high P-T phase diagrams. • First complete thermodynamic database for solid phases of 13 common transition metals was created. This database has: All the thermochemical data on these elements in their standard state (mostly available and compiled); All the equations of state (EoS) formulated from pressure-volume-temperature data (measured as a part of this study and from literature); Complete thermodynamic data for selected elements from standard to extreme conditions. The thermodynamic database provided by this study can be used with available thermodynamic software to calculate all thermophysical properties and phase diagrams at high P-T conditions. For readers who do not have access to this software, tabulated values of all thermodynamic and volume data for the 13 metals at high P-T are included in the APPENDIX. In the APPENDIX, a description of several other high-pressure studies of selected oxide systems is also included. Thermophysical properties (Cp, H, S, G) of the high P-T ω-phase of Ti, Zr and Hf were determined during the optimization of the EoS parameters and are presented in this study for the first time. These results should have important implications in understanding hexagonal-close-packed to simple-hexagonal phase transitions in transition metals and other materials.

Geochemistry of transition, non-transition and rare-earth elements in the surficial sediments of continental shelf of Kerala and an annex to the Cochin estuarine system

The metals present in the surface sediments have high demand on a global perspective, and the main reservoir of these elements is believed to be the ocean floor. A lot of studies on metals are going on throughout the world for its quantification and exploitation. Even though, some preliminary attempts have been made in selected areas for the quantitative study of metals in the western continental shelf of India, no comprehensive work has been reported so far. The importance of this study also lies on the fact that there has not been a proper evaluation of the impact of the Great Tsunami of 2004 on the coastal areas of the south India. In View of this, an attempt has been made to address the seasonal distribution, behavior and mechanisms which control the deposition of metals in the sediments of the western continental shelf and Cochin Estuary, an annex to this coastal marine region.Surface sediment samples were collected seasonally from two subenvironemnts of southwest coast of India, (continental shelf of Kerala and Cochin estuarine system), to estimate the seasonal distribution and geochemical behavior of non-transition, transition, rare-earth elements, Th and U. Bottom water samples were also taken from each station, and analysed for temperature, salinity and dissolved oxygen, hence the response of redox sensitive elements to oxygen minimum zone can be addressed. In addition, other sedimentary parameters such as sand, silt, clay fractions, CaCO3 and organic carbon content were also estimated to evaluate the control factors on level of metals present in the sediment. The study used different environmental data analysis techniques to evaluate the distribution and behavior of elements during different seasons. This includes environmental parameters such as elemental normalisation, enrichment factor, element excess, cerium and europium anomalies and authigenic uranium.

Studies in the mass spectra of perfluoroaromatic derivatives of phosphorus and some selected transition metals

The mass spectra and fragmentation of a variety of fluoroaromatic compounds of Group V and some selected transition elements are discussed in some detail, aided by data from metastable defocussed experiments. Results of ,studies on the coupling reaction using unstable organotitanium chloride intermediate species are reported. The preparation of some 5-substituted octafluorodibenzophospho1es is also discussed. Rearrangements under electron bombardment resulting in the loss of heteroatom-fluoride fragments are discussed in the light of presently accepted mechanisms for these processes as are rearrangements observed in compounds involving thionophosphoryl bonds ( p=s ).

Mo and W bis-MGD enzymes: nitrate reductases and formate dehydrogenases

J Biol Inorg Chem (2004) 9: 791–799 DOI 10.1007/s00775-004-0573-9

Flow injection analysis (FIA) determination of lead by hydride generation in banded coral skeletons /

A flow injection hydride generation direct current plasma atomic emission spectrometric (FI-HG-DCP-AES) method was developed for the determination of lead at ng.ml-l level. Potassium ferricyanide (K3Fe(CN)6) was used along with sodium tetrahydroborate(III) (NaBH4) to produce plumbane (PbH4) in an acid medium. The design of a gas-liquid separator (hydride generator) was tested and the parameters of the flow injection system were optimized to achieve a good detection limit and sample throughput. The technique developed gave a detection limit of 0.7 ng.ml-l(3ob). The precision at 20 ng.ml"* level was 1.6 % RSD with 1 1 measurements (n=l 1). Volume of sample loop was 500 |J.l. A sample throughput of 120 h"^ was achieved. The transition elements, Fe(II), FeOH), Cd(n), Co(II), Mn(n), Ni(II) and Zn(n) do not interfere in this method but 1 mg,l'l Cu(II) will suppress 50 % of the signal from a sample containing 20 ng.ml'l Pb. This method was successfully applied to determine lead in a calcium carbonate (CaC03) matrix of banded coral skeletons from Si-Chang Island in Thailand.

L’impact de l’unité centrale sur les propriétés optoélectroniques d’imino-thiophènes électrochromes : s ynthèse et caractérisation

De nouvelles molécules électrochromes à base de thiophène et comportant des liaisons azométhine ont été synthétisées et caractérisées afin d’étudier les relations entre leur structure et leurs propriétés. Le but premier de cette étude a été d’obtenir plus d’information pouvant guider le développement de nouvelles molécules électrochromes performantes à l’aide d’une meilleure compréhension de ce qui influence leurs caractéristiques. La synthèse a été réalisée en évitant l’emploi de conditions réactionnelles difficiles et les quantités d’éléments de transition ont été minimisées. Les nouvelles structures ont permis de vérifier l’effet de la variation de l’unité centrale sur les propriétés finales. Les modifications ont principalement porté sur la longueur effective de conjugaison par l’ajout d’unités de thiophène, ainsi que l’incorporation d’une liaison vinylique. L’effet de la présence de chaînes alkyles sur les positions C3 et C4 des thiophènes du coeur de chaque molécule a également été étudié. Les propriétés telles le potentiel d’oxydation, le nombre d’électrons échangés, la réversibilité des phénomènes d’oxydoréduction, l’absorbance, ainsi que l’électrochromisme chimique et électrochimique ont été étudiées, principalement par voltampérométrie cyclique et spectrométrie UV-visible en solution. De plus, des calculs théoriques ont été effectués afin d’appuyer les résultats obtenus expérimentalement. La modification du coeur de la molécule par ajout de thiophènes voisins n’a pas entraîné de grand déplacement bathochrome du λAbs, et dans le cas des thiophènes dialkylés, un déplacement hypsochrome d’au moins 66 nm a eu lieu causé par la torsion du squelette. L’étude des structures à l’état solide a même révélé l’obtention d’un nouveau composé possédant des propriétés vapochromiques prononcées. Les nouveaux composés électrochromes possèdent des valeurs de λAbs allant de 431 à 513 nm, et des potentiels d’oxydation de 0,8 à 1,2 V.

Tailored Ion Imprinted Polymer Materials for the Preconcentrative Separation of Noble Metals

Tailored ion imprinted polymer materials for the preconcentrative separation of noble metals. This study deals with the synthesis, separation,characterization and analytical application of the noble metals especially palladium and platinum. Platinum group metals(PGM) are currently receiving world wide attention. This group include Palladium(Pt),rhodium(Rh), ruthenium(Ru), iridium(Ir) and osmium(Os).PGM are used as catalysts for a wide variety of hydrogenation, oxidation, isomerization,cyclization,dehydrogenation and dehalogenation reactions.The corrosion resistance of PGM enables them to use in jewellery,electrical and glass industries,extrusion of synthetic fibres,manufacture of laboratory utensils,dental and medical devices. This study clearly establishes selective recovery of platinum from other noble and transition elements.

Computational studies on the structure and stabilities of magnetic inter-metallic compounds

The purpose of this thesis is to further the understanding of the structural, electronic and magnetic properties of ternary inter-metallic compounds using density functional theory (DFT). Four main problems are addressed. First, a detailed analysis on the ternary Heusler compounds is made. It has long been known that many Heusler compounds ($X_2YZ$; $X$ and $Y$ transition elements, $Z$ main group element) exhibit interesting half-metallic and ferromagnetic properties. In order to understand these, the dependence of magnetic and electronic properties on the structural parameters, the type of exchange-correlation functional and electron-electron correlation was examined. It was found that almost all Co$_2YZ$ Heusler compounds exhibit half-metallic ferromagnetism. It is also observed that $X$ and $Y$ atoms mainly contribute to the total magnetic moment. The magnitude of the total magnetic moment is determined only indirectly by the nature of $Z$ atoms, and shows a trend consistent with Slater-Pauling behaviour in several classes of these compounds. In contrast to experiments, calculations give a non-integer value of the magnetic moment in certain Co$_2$-based Heusler compounds. To explain deviations of the calculated magnetic moment, the LDA+$U$ scheme was applied and it was found that the inclusion of electron-electron correlation beyond the LSDA and GGA is necessary to obtain theoretical description of some Heusler compounds that are half-metallic ferromagnets. The electronic structure and magnetic properties of substitutional series of the quaternary Heusler compound Co$_2$Mn$_{1-x}$Fe$_x$Si were investigated under LDA+$U$. The calculated band structure suggest that the most stable compound in a half-metallic state will occur at an intermediate Fe concentration. These calculated findings are qualitatively confirmed by experimental studies. Second, the effect of antisite disordering in the Co$_2$TiSn system was investigated theoretically as well as experimentally. Preservation of half-metallicity for Co$_2$TiSn was observed with moderate antisite disordering and experimental findings suggest that the Co and Ti antisites disorder amounts to approximately 10~% in the compound. Third, a systematic examination was carried out for band gaps and the nature (covalent or ionic) of bonding in semiconducting 8- and 18-electron or half-metallic ferromagnet half-Heusler compounds. It was found that the most appropriate description of these compounds from the viewpoint of electronic structures is one of a $YZ$ zinc blende lattice stuffed by the $X$ ion. Simple valence rules are obeyed for bonding in the 8- and 18-electron compounds. Fourth, hexagonal analogues of half-Heusler compounds have been searched. Three series of compounds were investigated: GdPdSb, GdAutextit{X} (textit{X} = Mn, Cd and In) and EuNiP. GdPdSb is suggested as a possible half-metallic weak ferromagnet at low temperature. GdAutextit{X} (textit{X} = Mn, Cd and In) and EuNiP were investigated because they exhibit interesting bonding, structural and magnetic properties. The results qualitatively confirm experimental studies on magnetic and structural behaviour in GdPdSb, GdAutextit{X} (textit{X} = Mn, Cd and In) and EuNiP compounds. ~

57 Fe and 119 Sn Mössbauer studies on new Heusler compounds for spintronic applications

Seit der Entwicklung einer großen Vielfalt von Anwendungsmöglichkeiten der Spintronik auf Basis von Heusler Verbindungen innerhalb der letzten Dekade kann der Forschungsfortschritt an dieser Material Klasse in einer Vielzahl von Publikationen verfolgt werden. Eine typische Heusler Verbindung X2YZ besteht aus zwei Übergangsmetallen (X, Y) und einem Hauptgruppenelement (Z). Diese Arbeit berichtet von Heusler Verbindungen mit besonderem Augenmerk auf deren potentielle halbmetallische Eigenschaften und davon insbesondere solche, die eine richtungsabhängige magnetische Anisotropie (perpendicular magnetic anisotropy- PMA) zeigen könnten. PMA ist insbesondere für Spin transfer Torque (STT) Bauelemente von großem Interesse und tritt in tetragonalrnverzerrten Heusler Verbindungen auf. Bei STT-Elementen werden mittels spinpolarisierter Ströme die magnetische Orientierung von magnetischen Schichten beeinflusst.rnDie signifikantesten Ergebnisse dieser Arbeit sind: die Synthese neuer kubischen Heusler Phasen Fe2YZ, die theoretisch als tetragonal vorausgesagt wurden (Kapitel 1), die Synthese von Mn2FeGa, das in der tetragonal verzerrten Struktur kristallisiert und Potential für STT Anwendungen zeigt (Kapitel 2); die Synthese von Fe2MnGa, das einen magnetischen Phasenübergang mit exchange-bias (EB) Effekt zeigt, der auf einer Koexistenz von ferromagnetischen (FM) und antiferromagnetischen (AFM) Phasen beruht (Kapitel 3); Schlussendlich wird in Kapitel 4 die Synthese von Mn3−xRhxSn diskutiert, in welcher insbesondere tetragonales Mn2RhSn als potentielles Material für Anwendungen in derrnSpintronik vorgestellt wird.rnIn dieser Arbeit wurden hauptsächlich Heusler Verbindungen mit mößbaueraktiven Elementen 57Fe und 119Sn, synthetisiert und untersucht. Im Falle der hier untersuchten Heusler Verbindungen spielt die Charakterisierung durch Mößbauer Spektroskopie eine entscheidende Rolle, da Heusler Verbindungen meistens ein gewisses Maß an Fehlordnung aufweisen, welche deren magnetischen und strukturellen Eigenschaften beeinflussen kann. Die Art der Fehlordnung jedoch kann nur schwer durch standard Pulver-Röntgendiffraktion bestimmt werden, weshalb wir die Vorteile der Mößbauer Spektroskopie als lokale Methode nutzen, um den Typ und den Grad der Fehlordnung aufzuklären. rnDiese Arbeit ist wie folgt gegliedert:rnIn Kapitel 1 wurden die neuen, kubisch-weichferromagnetischen Heuslerphasen Fe2NiGe, Fe2CuGa und Fe2CuAl synthetisiert und charakterisiert. In vorangegangenen theoretischen Studien wurde für deren Existenz in tetragonaler Heuslerstruktur vorhergesagt.rnUngeachtet dessen belegten unsere experimentellen Untersuchungen, dass diese Verbindungen hauptsächlich in der kubischen invers Heusler(X-) struktur mit unterschiedlichen Anteilen an atomarer Fehlordnung kristallisieren. Alle Verbindungen sind weiche Ferromagneten mit hoher Curietemperatur bis zu 900K, weswegen alle als potentielle Materialien für magnetische Anwendungen geeignet sind. In Kapitel 2 wurde Mn2FeGa synthetisiert. Es zeigte sich, dass Mn2FeGa nach Temperatur Nachbehandlung bei 400°C die invers tetragonale Struktur (I4m2) annimmt. Theoretisch wurde die Existenz in der inversen kubischen Heuslerstruktur vorausgesagt. Abhängig von den Synthesebedingungen ändern sich die magnetischen und strukturellen Eigenschaften von Mn2FeGa eklatant. Deshalb ändert sich die Kristallstruktur von M2FeGa bei Temperung bei 800 °C zu einer pseudokubischen Cu3Au-artigen Struktur, in welcher Fe- und Mn-Atome statistisch verteilt vorliegen. Dieser Übergang der Kristallstrukturen wurde durch Mößbauer Spektroskopie anhand des Vorliegens oder Fehlens der Quadrupolaufspaltung im Falle der invers tetragonalen bzw. pseudokubischen Modifikation nachgewiesen. In Kapitel 3 wurde Fe2MnGa ebenfalls erfolgreich synthetisiert und durch verschiedene Methoden charakterisiert. Der Zusammenhang von Kristallstruktur und magnetischen Eigenschaften wurde durch verschiedene Temperungskonditionen und mechanischer Behandlung untersucht. Der Schwerpunkt lag auf einer geschmolzenen Probe ohne weitere Temperung, die einen FM-AFM Phasenübergang zeigte. Diese magnetische Phasenumwandlung führt zu einem starken EB-Verhalten, welches seinen Ursprung hauptsächlich in der Koexistenz von FM- und AFM-Phasen unterhalb der FMAFM- Übergangstemperatur hat. Kapitel 4 ist den neuen Mn-basierten Heusler-Verbindungen Mn3−xRhxSn gewidmet, bei denen wir versuchten, durch den Austausch von Mn durch das größere Rh eine Umwandlung zu einer tetragonalen Struktur von den hexagonalen Mn3Sn-Struktur zu erreichen. Als interessant stellten sich Mn2RhSn und Mn2.1Rh0.9Sn heraus, da sie aus nur einer Phase vorzuliegen scheinen, wohingegen die anderen Verbindungen aus gemischten Phasen mit gleichzeitiger starken Fehlordnung bestehen. Im abschließenden Anhang wurden die Fehlordnung und gelegentliche Mischphasen einer großen Auswahl von Mn3−xFexGa Materialien mit 1≤x≤3, dokumentiert.rn

(Table 1) Sediment descriptions and age at DSDP Legs 5 and 63 Holes

Sediments from immediately above basalt basement and from between sections of basalt recovered from Deep Sea Drilling Project Legs 5 and 63 were analyzed by atomic absorption spectroscopy for Mg, Al, Si, Ca, Mn, Fe, Co, Ni, Cu, Zn, and Ba. All of these sediments showed enrichment in Fe and Mn over values typical of detritus supplied to the northeastern Pacific Ocean. X-ray diffractometry and differential chemical leaching indicate that up to 50% of the sediment, by weight, is in amorphous phases and that these phases are rich in Mn, Co, Cu, Ni, and Zn. Multivariate statistical analysis and normative partitioning of the chemical data indicate that much of the excess Fe and other transition elements in the sediment originate from hydrothermal sources.