Compounds Of Transition Elements Research Articles

A Study on Radiation Shielding Abilities of Some Compounds of 3d Transition Elements by Using Phy-X/PSD Code

In the present study, it was aimed to calculate the radiation-matter interaction parameters of some compounds of 3d transition elements. The radiation attenuation parameters, which are important to have knowledge about the radiation shielding potentials, were calculated by using Phy-X/PSD code in the energy range of 0.01-15 MeV. The calculated mass attenuation coefficient and effective atomic number results were compared with the experimental data which were measured at 19.63 and 22.10 keV previously and, a good agreement was achieved. In order to evaluate the shielding properties of the compounds, we also compared the mass attenuation coefficients of the compounds with ordinary concrete, steel-scrap, ilmenite-limonite and basalt-magnetite, which are widely used as radiation protective materials. According to the obtained results, it is concluded that the studied compounds have radiation shielding potentials.

Photoionization Dynamics of the Tetraoxo Complexes OsO4 and RuO4.

The photoionization dynamics of OsO4 and RuO4, chosen as model systems of small-size mononuclear heavy-metal complexes, has been theoretically studied by the time-dependent density functional theory (TDDFT). Accurate experimental measurements of photoionization dynamics as a benchmarking test for the theory are reported for the photoelectron asymmetry parameters of outer valence ionizations of OsO4, measured in the 17–90 eV photon energy range. The theoretical results are in good agreement with the available experimental data. The observed dynamical behavior of partial cross sections and asymmetry parameters has been related to both the coupling to the continuum of discrete excited states, giving strong modulations in the photon energy dependency, and the atomic composition of the initial ionized states, which determines the rate of decay of ionization probability for increasing excitation energies. Overall, an extensive analysis of the photoionization dynamics for valence and core orbitals is presented, showing good agreement with all the available experimental data. This provides confidence for the validity of the TDDFT approach in describing photoionization of heavy transition element compounds, with the perspective of being used for larger systems. Further experimental work is suggested for RuO4 to gather evidence of the sensitivity of the theoretical method to the nature of the metal atom.

Morphology and phase control of iron oxide polymorph nanoparticles

In this work, lepidocrocite (γ-FeOOH) nanobundles were prepared by a facile NH4F assisted epoxide precipitation route. The reactions between epoxide and [Fe(H2O)6]2+ promoted the hydrolysis and condensation of [Fe(H2O)6]2+, resulting in the formation of iron oxyhydroxide. After calcination of γ-FeOOH nanobundles at 400 °C, the produced α-Fe2O3 still kept the bundle morphology. Due to the unique chemistry of epoxide, the morphology and phase of iron oxide polymorph nanoparticles (goethite, akaganeite, lepidocrocite, magnetite) were well-controlled through controlling reaction conditions such as Fe2+ concentration, NH4F additive and reaction temperature. It is particularly interesting that NH4F working as phase controlling agent is able to control the phase development of iron oxyhydroxides. This phase control effect of NH4F is attributed to the promoted reaction rate of epoxide originating from the higher electronegativity of fluoride ions than chloride ions. Based on the results in this work and our other preliminary works, it is considered that this route can be used as a general strategy for controlling the morphology and phase of transition element compounds.

X-ray circular magnetic dichroism in the presence of strong spin fluctuations

The use of X-ray magnetic circular dichroism (XMCD) spectra for determininghe t magnitude of atomic magnetic moments in compounds of rare-earth and transition elements is discussed. The standard sum rule approach often yields a magnitude of moments that is often smaller than values obtained from magnetic measurements. We attribute this to strong spin fluctuations in the surface layers in which XMCD signals form. A way of determining the values of local magnetic moments in the presence of strong fluctuations is proposed and tested.

Fifty Years of Conferences on Solid Compounds of Transition Elements

The first conference on what became the SCTE series was organized by André Michel in Paris in 1965. It was intended to deal with the preparation and Propriétés Thermodynamiques, Physiques et Structurales des Dérivés Semi-Métalliques. The results of experimental as well as theoretical investigations were reported by inorganic chemists, physicists, and crystallographers. Originally, the emphasis was on compounds of the transition metals, the rare earth elements, and the actinoids with the main group elements S, Se, Te, N, P, As, Sb, C, Si, Ge, Sn, and boron. Work on oxides and halides was presented only occasionally. Over the years this has changed gradually. Now investigations of oxides comprise some 10 to 20 % of all reports, especially investigations of compounds with small band gaps and interesting physical properties. The emphasis is shifting from fundamental research to investigations with a view on applications.

Study of the effect of compounds of transition elements on the micellar catalysis of strength formation of reactive powder concrete

Changes in the rate of cement hydration affect the rate of concrete compressive strength formation. Under certain conditions, an increase in the cement hydration rate improves the concrete compressive strength. This is especially true for reactive powder concretes. The paper studies the effect of micellar solutions, consisting of a mixture of a micelle-forming surfactant and compounds of transition elements. A feature of the study was investigating the simultaneous effect of micelle-forming surfactants and compounds of transition elements on the change in the concrete strength. The study found that given micellar solutions and compounds of transition elements alter the nature of the concrete strength formation, namely increase the rate of strength formation of reactive powder concretes in the initial period due to micellar catalysis of cement hydration and maintain increased compressive strength at later stages of hardening through the impact of compounds of transition elements, formation of minerals, containing high amount of chemically-bound water. It is proved that micellar catalysis can be used to control the processes of cement hardening and strength formation of artificial stone, produced in the cement hydration, thereby reducing the time to achieve the concrete design strength and increasing the absolute value of compressive strength of such concretes at 28 days using compounds of transition elements.

International Conference on Solid Compounds of Transition Elements (SCTE2012)

International Conference on Solid Compounds of Transition Elements (SCTE2012)

Electrochemical Synthesis of Complex Compounds of Transition Elements with Carboxyl- and Carbonyl-containing Ligands

Complex compounds of d- and f-elements with carboxyl- and carbonyl-containing ligands were synthesized by the electrochemical method. The influence exerted by a number of factors on the process course was studied. The dependence of the electrosynthesis parameters on the composition of the forming compounds was established. The composition of these compounds was determined. A new method for anodic synthesis of these compounds was developed.

Magnetism of L1 compounds with the composition MT (M=Rh, Pd, Pt, Ir and T=Mn, Fe, Co, Ni)

The electronic band structure of ordered equiatomic compounds of 3d transition elements (Mn, Fe, Co, Ni) with nonmagnetic 4d and 5d elements (Rh, Pd, Pt, Ir) are investigated by linear muffin-tin orbital calculations. The systematic study considers 3d and 4d/5d spin moments and interatomic exchange interactions, with emphasis on the comparison between ferromagnetic and antiferromagnetic order. Total and site-resolved exchange interactions are calculated from first principles, and the obtained exchange constants are used to estimate ordering temperatures on a mean-field level.

HYBRIDIZATION EFFECTS IN SOME UTSi (2:1:3; 1:1:1; 2:3:1) COMPOUNDS

The presence of magnetic moments in uranium atoms in some of U 2 TSi 3, UTSi and U 2 T 3 Si ( T is a 3d, 4d or 5d transition element) compounds is discussed in terms of the hybridization of s, p, d and f atomic orbitals. The hybridization strength in these ternary series of isostructural compounds was calculated using the semiquantitative band structure approach of Straub and Harrison. The prediction criterion for the presence of magnetic ordering, comparing the band width with a critical energy, seems to hold. The dominant influence of fd hybridization effects in the change of magnetic properties inside an isostructural group is in evidence.

Zinc-blende compounds of transition elements with N, P, As, Sb, S, Se, and Te as half-metallic systems

We report systematic first-principles calculations for ordered zinc-blende compounds of the transition metal elements V, Cr, Mn with the sp elements N, P, As, Sb, S, Se, Te, motivated by recent fabrication of zinc-blende CrAs, CrSb, and MnAs. They show ferromagnetic half-metallic behavior for a wide range of lattice constants. We discuss the origin and trends of half-metallicity, present the calculated equilibrium lattice constants, and examine the half-metallic behavior of their transition element terminated (001) surfaces.

ChemInform Abstract: Optically Active Organometallic Compounds of Transition Elements with Chiral Metal Atoms

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Optically Active Organometallic Compounds of Transition Elements with Chiral Metal Atoms.

Chiral transition metal atoms are not only present in tris-chelate complexes [M(LL)3 ]n+ , which were already resolved into the enantiomers by Alfred Werner, but also in organometallic half-sandwich complexes such as 1 with three- or four-legged piano-stool structure. These complexes have been tools in the elucidation of the spatial course of reactions and in organic syntheses. Applications in enantioselective catalysis are beginning to show up.

Chemical Effects on the Kβ/KαIntensity Ratios in First-Row Transition Element Compounds

Chemical Effects on the K_β/K_αIntensity Ratios in First-Row Transition Element Compounds

Relationship between phenomenological crystal field parameters and the crystal structure: The simple overlap model

The simple overlap model is used to calculate crystal field parameters from the crystal structure. It is applied to 25 rare earth and some actinide and 3d transition element compounds for which crystal field parameters have been previously determined experimentally. The model is based on effective charges, located around the middle of the rare earth ion–ligand distance, which are assumed to be proportional to the magnitude of the overlap, ρ, between the rare earth ion and ligand wavefunctions. Good agreement between theoretical and experimental crystal field parameters is found for most of the cases studied. The best predictions are obtained when the overlap varies slightly from one rare earth compound to another (0.05<ρ<0.08), in agreement with the general assumption that the f orbitals have a small part in the chemical bonding. For the two examples involving the 5f elements, the overlaps with the ligand have, curiously, the same magnitude as in the case of the rare earth elements. As expected, the 3d element wavefunctions show a stronger mixing with those of the ligands (0.10<ρ<0.25).

Newly Developed Decontamination Technology Based on Gaseous Reactions Converting to Carbonyl and Fluoric Compounds

A new gas-phase decontamination technology is developed based on gaseous reactions utilizing the volatile properties of the carbonyl and fluoric compounds of radioactive transition elements and actinides (corrosion products, fission products, and transuranium) on a material’s surface. The feasibility of this new technology is determined by removing nonradioactive (Co, Cr, Ni, Re, Mo, Mn, Ru, and Zn) and radioactive (60Co, 63Ni, and 103Ru) nuclide transition elements as gaseous forms under high CO pressure (50 to 200 atm) and high temperature (~350°C). Experiments involving U and using fluoric gases are also performed. For radioactive nuclides existing in an oxide layer of stainless steel, pretreatment with supercritical CO2 + I2 + H2O is used to remove the oxide layer completely, and by the subsequent gaseous reaction, 95 to 99% of 60Co is removed from the layer by CO gas treatment at a pressure of 200 atm. The plasma treatment using fluorine gas results in U being removed with high efficiency (~60%) after only 5 min, even at a reduced pressure of 1 Torr and at room temperature. When the carbonyl and fluoric species generated from a nontoxic gas mixture (1 Torr) of CF4 and O2 is used, U and 60Co are removed simultaneously with high removal efficiencies of 80 and 100% for 60Co and U, respectively. The data provide evidence that chemically reactive plasma treatment is available as a gas-phase decontamination method that can be conducted using nontoxic gases under safe and mild conditions such as reduced pressure, shorter time periods, and ambient temperature. Finally, a fluoric chemical reaction can be used to remove solid U deposits by converting them to gaseous U compounds at room temperature and without using plasma treatment. The pressure of ClF3 gradually affects the higher removal efficiency of U, and the removal efficiency is >90% under the conditions of 30 min and >100 Torr. The results verify that chemical reactions involving carbonylation and fluorination reactions can be utilized for gas-phase decontamination, and the potential for this new idea for decontamination is affirmed.If gas-phase decontamination technology is further developed, it will be not only convenient but also economically advantageous because decontaminating and treating the large volume of nuclear wastes - especially nonincinerable radioactive wastes - are currently very difficult.

Investigation of the pre-edge inelastic X-ray scattering by several 3d transition-metal compounds

Abstract Spectra of X-rays scattered by compounds of 3d transition elements exhibit structure when the energies of the incident X-rays are a few electronvolts below the elements' K-absorption edge energies. This structure is the result of an inelastic scattering process and has been studied in compounds of chromium, iron and copper with a high-energy resolution wavelength-dispersive spectrometer. When the energies of the incident X-rays were tuned between the preedge peak and the absorption edge, the energy of the resonantly scattered X-rays were always measured to be equal to the energy of the characteristic Kα X-rays. This observation is in disagreement with the prediction of the present theoretical models for resonant scattering which were derived assuming the interactions to be fast collisions.

INFLUENCE OF d-ORBITAL OCCUPANCY ON THE GEOMETRY OF PENTACOORDINATED MOLECULES

Abstract A quantitative assessment of solid-state structural data on five coordinated compounds of both transition and main group elements establishes the geometrical change in the square pyramid as a function of d-orbital configuration. In terms of the trans basal angle θ, a variation in the range 140–174° is obtained. These angle variations are interpreted in terms of nonbonded repulsions between d-orbital electron density and bond electron density. Structural distortion from the trigonal-bipyramidal and square-pyramidal geometries are determined for the five-coordinated compounds by using a dihedral angle method. It is found that the local distortion coordinate for transition-metal complexes approximates the Berry intramolecular exchange coordinate. Main group pentacoordinated compounds follow this coordinate more closely.

ChemInform Abstract: Reactions of 2,4,6‐Tris(trifluoromethyl)phenols with Compounds of Main Group (Li, Na, Mg, Ca, Ba, Ge, Sn) and Transition (Ti, W, Mn, Cd) Elements.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Charge distribution and local and non‐local screening effects studied by means of the Auger parameter and chemical state plots

AbstractCopper‐ and zinc‐containing compounds, as well as other 3dn transition metal compounds, are characterized by making use of two concepts introduced first by Wagner: the Auger parameter, α = EB (photoelectron) + EK (Auger), and the so‐called chemical state plots (EK vs. EB, with the binding energy in the negative direction on the abscissa and the Auger parameter on a diagonal grid with slope equal to +1). These are useful tools to obtain information on: (1) the relative initial state charge distributions; and on (2) the relative extra‐atomic relaxation energy in the final state.In the present paper, for the first time, we show that the Auger parameter can also be helpful in the analysis of the screening mechanism in transition metal compounds.The position in the chemical state plots of different classes of compounds is discussed. The constancy of the Auger parameter for Cu(II) compounds is interpreted as further evidence of the electronic nature of the 2p3/2 final state. It can be represented by a 2p53d10L electronic structure, a local screended final state, where a charge transfer from the ligand valence orbitals toward localized d‐orbitals allows screening of the core‐hole. For copper, this relaxation energy is similar to the screening energy in the metallic state.For Cu(I) compounds, as in the case of Zn(II) compounds (d10 electronic configuration), a large dependence of the Auger parameter on the chemical nature of the ligands suggests a non‐local screening mechanism in the final state, i.e. a strong influence of electronic polarizability of the ligands on the relaxation energy. In this case, the extended s‐p cation orbitals are involved in the screening process.The charge distribution in the initial state can be studied analytically or by using chemical state plots. For example, Cu(II) compounds have about a constant Auger parameter (they fall on the same diagonal line with slope equal to +1), with the more ionic compounds at higher 2p3/2 binding energy and lower (L3M45M45, 1G) Auger kinetic energy.It appears that the Auger parameter and the chemical state plots permit an accurate characterization of the ground‐state electronic structure of cations in transition element compounds and of the screening mechanism in the final state.