Relaxation phenomena involved in the L3M4,5M4,5;1G4 auger process in zinc metal

A detailed analysis is presented of the L₃M_4,5M_4,5;¹G₄ Auger transition in metallic zinc. An extra-atomic relaxation term, neglected until now, is taken into account. This results in excellent agreement between calculated and experimental values of the Auger-transition energy.     

Study of M4,5N4,5N4,5 auger energy shifts of Cs and I in free CsI molecules

High-resolution electron beam excited M_4,5N_4,5N_4,5 Auger electron spectra of Cs and I have been measured from CsI vapour. The Auger energies of both Cs and I observed from gaseous CsI are higher than the corresponding free-atom energies due to extra-atomic relaxation. The molecular Auger results have been compared with corresponding photoelectron measurements and free-atom data. Estimates for extra-atomic relaxation energies have been extracted from the changes of the Auger parameter between molecular and atomic species and from the difference between experimental energies and energies calculated with a relativistic Dirac-Fock program, applying the point-charge model for the CsI molecule.     

X-ray photoelectron emission studies of mixed selenides AgGaSe2 and Ag9GaSe6

Auger and direct electron specta from crystalline AgGaSe₂ and Ag₉GaSe₆ have been studied with X-ray photoelectron spectroscopy. It is shown that the AgM₅N_4,5N_4,5 and M₄N_4,5N_4,5 Auger spectra are more sensitive to the chemical environment than the Ag 3d direct photoelectron spectra. Furthermore the Auger parameter as defined by Wagner is used in order to characterize the chemical state of these compounds. Last, the XPS spectra of the valence-band region are investigated and chalcogen s and p and noble-metal d bands are clearly identified. The electronic structure of these two selenides does not seem to be determined predominantly by the crystal structure. As a whole, the spectral features are discussed in connection with the character of the chemical bonding and the physical properties of these compounds.     

Configuration interaction in the L2,3—MM Auger spectrum of HCl and Ar

The L_2,3—MM Auger spectra of HCl and Ar have been calculated. Strong interaction between the Auger diagram state 4σ^?2 and correlation states explains the absence of the L_2,3—M₁² peak in the HCl spectrum. For argon semi-internal CI reproduces the high-kinetic-energy region, while a fairly large expansion of configurations is necessary to reproduce the low-kinetic-energy part of the spectrum.     

Oxygen analysis of O2MF6 and O2M2F11 salts

The dioxygenyl salts O₂MF₆ or O₂M₂F₁₁ where M = As, Sb, Bi, Nb, Ta, Ru, Au, and Pt, were hydrolysed aqueous base (40% NaOH) to evaluate their purity and to gain further information about their thermal instability. Compounds containing As, Sb, Bi, Nb and Ta yielded 1.25 moles O₂ per mole of starting material whereas for compounds containing Ru, Au and Pt, 1.5 moles of O₂ per mole of salt was produced. The difference is a consequence of the greater oxidizing power of the RuF^-₆, AuF^-₆ and PtF^-₆ anions. All of the dioxygenyl salts are intrinsically unstable at room temperature in vacuum.     

SCF discrete-variational Xα calculations of the NH4Cl Auger spectrum

Formalism for calculations of the singlet and triplet Auger energies within the Xα model is presented. Using this method the KVV Auger spectrum of NH₄Cl is calculated and the theoretical intensities are determined within a one-center approximation. The calculated spectrum reproduces quite well all the main features observed for solid NH₄Cl. A new interpretation of the spectrum is suggested.     

Synthesis and structural characterization of novel tin and titanium potassium silicates K4M2Si6O18

The synthesis of a new potassium titanosilicate, K₄Ti₂Si₆O₁₈ (Ti-AV-11), possessing the crystal structure of potassium stannosilicate AV-11, has been reported. The unit cell of this material is trigonal, space group R3 (no. 146), Z=3, a=10.012, c=14.8413 Å, γ=120°, V=1289 Å³. The structure of AV-11 is built up of MO₆ (M=Sn, Ti) octahedra and SiO₄ tetrahedra by sharing corners. The SiO₄ tetrahedra form helix chains, periodically repeating every six tetrahedra. These chains extend along the [001] direction and are linked by isolated MO₆ octahedra, thus producing a mixed octahedral-tetrahedral oxide framework. AV-11 materials have been further characterized by bulk chemical analysis, powder X-ray diffraction (XRD), scanning electron microscopy (SEM), ²⁹Si and ¹¹⁹Sn magic-angle spinning (MAS) NMR spectroscopy.     

Antimony(V) catecholato complexes based on 4,5-dialkylsubstituted o-benzoquinone. The spectroscopic and electrochemical studies. Crystal structure of [Ph4Sb][Ph2Sb(4,5-Cat)2]

Triphenylantimony(III) and triethylantimony(III) readily react with 4,5-(1,1,4,4-tetramethyl-butane-1,4-diyl)-o-benzoquinone to form catecholato complexes R₃Sb(4,5-Cat) (R = Ph (1), Et (2); 4,5-Cat is dianionic 4,5-(1,1,4,4-tetramethyl-butane-1,4-diyl)-catecholate). In polar solvents (CHCl₃, acetone) complex 1 transforms easily to ionic complex compound [Ph₄Sb]⁺[Ph₂Sb(4,5-Cat)₂]⁻ (3) with diphenyl-bis-[4,5-(1,1,4,4-tetramethyl-butane-1,4-diyl)-catecholato]antimony(V) complex anion. Complexes were characterized by IR, ¹H, ¹³C NMR spectroscopy, cyclic voltammometry. Molecular structure of 3·CHCl₃ was confirmed by X-ray analysis. Cyclic voltammometry of 1 and 3 shows that both complexes undergo reversible one-electron oxidation to quite stable paramagnetic o-semiquinonato species [Ph₃Sb(4,5-SQ)]⁺ and [Ph₂Sb(4,5-SQ)(4,5-Cat)] (0.75 and 0.49 V in CH₂Cl₂ vs. Ag/AgCl/KCl, respectively).     

Hg2M2F6S et Hg2M2F6O: Deux nouvelles familles de pyrochlores contenant du mercure et des métaux M de transition divalents

New pyrochlore compounds Hg₂M₂F₆S (M = Zn, Cu, Ni, Co, Mn, Mg) and Hg₂M₂F₆O (M = Zn, Cu, Ni, Co, Mg) have been prepared and characterized. They all have a cubic structure (Fd3m) except Hg₂Cu₂F₆O, which shows a tetragonal distortion. Refinement of crystal structures of five compounds from powder diffractometer intensities leads to a positional parameter x(48f) lying from 0.315 to 0.319. The evolution of interatomic distances and independance of two networks (Hg₂X′)²⁺ and (M₂F₆)^2? are examined.     

Synthesis and electrical properties of Li1+ x M x Ti2– x (PO4)3 (where M =Sc, Al, Fe, Y; x =0.3) superionic ceramics

Compounds of the system Li_{1+ x} M _x Ti_{2– x} (PO₄)₃ (where M=Sc, Al, Fe, Y; x=0.3) were synthesized by a solid-state reaction and studied by X-ray diffraction. The ceramic samples were sintered and investigated by complex impedance spectroscopy in the frequency range 10⁶–1.2×10⁹ Hz in the temperature range 300–600 K. Two relaxation dispersions related to the fast Li⁺ ion transport in bulk and grain boundaries were found. The activation energies of the bulk conductivity and relaxation frequency were obtained from the slops of Arrhenius plots. The values of the activation energies of the bulk ionic conductivity and relaxation frequency were found to be very similar in all the materials investigated. That can be attributed to the fact that the temperature dependences of the bulk conductivity are caused only by the mobility of the fast Li⁺ ions, while the number of charge carriers remains constant with temperature. Electronic Publication     

Theoretical study of polyoxide clusters B20O30, Al20O30, V20O50, Si20O30H20, and Si20O30F20

The structural, electronic, and vibrational characteristics and energies of the isolated polyoxide clusters B₂₀O₃₀, Al₂₀O₃₀, V₂₀O₅₀, Si₂₀O₃₀H₂₀, and Si₂₀O₃₀F₂₀ and their complexes with the H⁻ ion and ammonia complexes Al₂₀O₃₀ · nNH₃ have been calculated by the density functional theory B3LYP method with different basis sets. The computation results show that the symmetric closo structure I _h with oxygen bridges located above the centers of the faces of an empty [M₂₀] dodecahedron is more favorable for V₂₀O₅₀, Si₂₀O₃₀H₂₀, and Si₂₀O₃₀F₂₀. For B₂₀O₃₀, the cage closo isomer is also more favorable than the other isomers, but its structure is severely distorted as compared to a dodecahedron and has a symmetry close to C ₃ . For Al₂₀O₃₀, the I _h structure corresponds to a high-lying local minimum of the potential energy surface. For Al₂₀O₃₀, a set of unusual puckshaped isomers of symmetry C _i , with different numbers of four-coordinate atoms ^IVAl and three-coordinate atoms ^IIIO, was localized; these structures are more than 90 kcal/mol more favorable than the dodecahedron I _h . The most favorable isomer of Al₂₀O₃₀ contains twelve four-coordinate atoms ^IVAl and four five-coordinate atoms ^VAl. The energies of dissociation of the most favorable M₂₀O₃₀ clusters into the M₂O₃ (C _2v ) and M₄O₆ (T _d ) fragments and, in the case of Al₂₀O₃₀, also into the Al₈O₁₂ (O _h ) and Al₁₂O₁₈ (D _3d ) fragments, have been estimated. The conclusion has been drawn that these clusters can, in principle, exist and can be experimentally detected in the isolated state. Analogous calculations have been performed for ammonia complexes Al₂₀O₃₀ · nNH₃ with n varying from 1 to 20. The effect of solvation on the relative stability of the dodecahedral and puckshaped isomers of the Al₂₀O₃₀ cluster is observed. The isomers with ammonia molecules in their first coordination sphere become much closer to one another on the energy scale; however, the dodecahedron remains a considerably less favorable intermediate. Original Russian Text ? O.P. Charkin, N.M. Klimenko, D.O. Charkin, 2008, published in Zhurnal Neorganicheskoi Khimii, 2008, Vol. 53, No. 4, pp. 624–635.     

Structure of two new borates YCa3(AlO)3(BO3)4 and YCa3(GaO)3(BO3)4

By replacing Mn in YCa₃(MnO)₃(BO₃)₄ with trivalent Al and Ga, two new borates with the compositions of YCa₃(MO)₃(BO₃)₄ (M=Al, Ga) were prepared by solid-state reaction. Structure refinements from X-ray powder diffraction data revealed that both of them are isostructural to gaudefroyite with a hexagonal space group P6₃/m. Cell parameters of a=10.38775(13)Å, c=5.69198(10)Å for the Al-containing compound and a=10.5167(3)Å, c=5.8146(2)Å for the Ga analog were obtained from the refinements. The structure is constituted of AlO₆ or GaO₆ octahedral chains interconnected by BO₃ groups in the ab plane to form a Kagomé-type lattice, leaving trigonal and apatite-like tunnels. It is found that most rare-earth and Cr, Mn ions can be substituted into the Y³⁺ and M³⁺ sites, respectively, and the preference of rare-earth ions to locate in the trigonal tunnel is correlated to the sizes of the M³⁺ ions.     

Formation of [CoCl4(H2O)2] complex in CoCl2·MgCl2·8H2O double salt: structural and energetic properties of [MCl4(H2O)2] and [M(H2O)6] (M=Mg, Co)

The crystal structure of the double salt CoCl₂·MgCl₂·8H₂O has been determined by the X-ray diffraction method. It crystallizes in the space group with a=6.0976(9), b=6.308(1), c=8.579(3) Å, α=81.99(2)°, β=88.40°, γ=84.61(1)°, Z=1, and R=0.027. The crystal consists of two kinds of well separated octahedra, [CoCl₄(H₂O)₂]²⁻ and [Mg(H₂O)₆]²⁺. The former is unique as aquachloro complexes of Co²⁺. In order to elucidate the reason prepared as such unique complexes in the double salts, formation energies for [MCl₄(H₂O)₂]²⁻ and [M(H₂O)₆]²⁺ (M=Co, Mg) have been calculated by using the density functional methods, and it has been revealed that the formation energies of the first coordination sphere for the metal ions and the Cl⁻?H₂O hydrogen bond networks around [CoCl₄(H₂O)₂]²⁻ play a decisive role in forming [CoCl₄(H₂O)₂]²⁻ with the regular octahedral geometry in the double salt.     

Solid-state decomposition studies on fluoroperoxo species of transition metals. Part VI. Kinetics of isothermal decomposition of M2Zr2(O2)2F6 · 2 H2O (M = Rb+, or Cs+)

The decomposition of solid fluoroperoxozirconates of alkali metals, M₂Zr₂(O₂)₂F₆ · 2 H₂O (M = Rb⁺, Cs⁺), is carried out in vacuum under isothermal conditions. The stoichiometry of the reaction may be represented by the equation, M₂Zr₂(O₂)₂F₆ · 2 H₂O(S) — M₂Zr₂O₂F₆(s) + O₂(g) + 2 H₂ O(g) (condensed). The fractional decomposition α is determined by measuring the pressure of oxygen evolved during pyrolysis with a McLeod gauge. The α values range from 0.06 to 0.70 for the rubidium and from 0.06 to 0.79 for the caesium species in the temperature ranges 107–202°C and 101–219°C, respectively. The α—time data for both compounds show that the kinetics are deceleratory throughout the course of the decomposition reaction. In both compounds, the initial stages of decomposition are described by a unimolecular decay law, while the later stages obey a contracting volume equation at all temperatures. The activation energies from Arrhenius plots are 14.0 and 10.9 kcal mole^?1 for the rubidium and 12.9 and 11.2 kcal mole^?1 for the caesium compound.     

Titanocene complexes of the N-methyl and N-phenyl-1,3-thiazoline-2-thione-4,5-dithiolates and 4,5-diselenolate ligands

Cp₂Ti(dithiolene) and Cp₂Ti(diselenolene) complexes containing the N-methyl-1,3-thiazoline-2-thione-4,5-dithiolate ligand (Me-thiazdt), the N-phenyl-1,3-thiazoline-2-thione-4,5-dithiolate ligand (Ph-thiazdt) and the N-methyl-1,3-thiazoline-2-thione-4,5-diselenolate ligand (Me-thiazds) have been synthesized. Three approaches have been developed in order to generate the dithiolene or the diselenolene ligands which were reacted with Cp₂TiCl₂ to form the corresponding heteroleptic complexes. Their X-ray crystal structures, UV-Vis absorption spectra as well as their redox properties, determined by cyclic voltammetry have been investigated and discussed. Variable-temperature ¹H NMR experiments have been performed in order to determine the activation energies of the chelate ring inversion.     

Photodissociation reaction CO−3

Photodissociation reaction CO^?₃ + hv → CO₂ + O^? has been observed at seven photon energies between 2.35 and 2.71 eV using a drift tube mass spectrometer and an argon ion laser. The total cross sections for the destruction of CO^?₃ due to photons of these energies have been measured, and it is concluded that essentially all of this destruction is due to photodissociation. The photodestruction of CO^?₃.H₂O has also been observed at four photon energies.     

The stereochemistry of Tutton's salts X2[M(H2O)6](YO4)2

Neutron structure determinations have been made of Tutton's salts, X₂[M(H₂O)₆] (YO₄)₂, where Y = Se, X = K⁺, M = Cu²⁺; Y = S, X = K⁺, M = Ni²⁺, Cu²⁺, Zn²⁺; X = Rb⁺, Cs⁺, M = Cu²⁺. This work has shown that there are extensive hydrogen networks with almost linear hydrogen bonds from [M(H₂O)₆]²⁺ to (YO₄)^2?. The (H … O) distance increases in the Cu²⁺ series for X = K⁺ to Cs⁺ but there is no difference for the potassium copper salts when Y = Se or S. Three different distorted [M(H₂O)₆]²⁺ octahedra were found in the series (orthorhombic, tetragonal with two long and four short, or four long and two short bonds). The interatomic distances from X⁺ to the neighboring O in a distorted XO₈⁺ dodecahedron increases with increased cation size, implying that the X⁺ polyhedron is maintaining its shape.     

Theoretical study of the 2Σu+ and 2Σg+ states of Li2− and Na2−

Ab initio calculations are performed to obtain potential energy curves for the X¹Σ_g⁺ state of Li₂ and Na₂ and the X²Σ_g⁺ and A²Σ_g⁺ states of their anions. The A²Σ_g⁺ M₂^? curves are found to intersect the X¹Σ_g⁺M₂ curves at low energies and are expected to play a major role in the e^? + M₂ → M^? + M process.     

Ordre local dans quelques verres fluores du systeme PbF2MIItF2MIIItF3 par EXAFS

The local environment of transition metal (M_t) and lead has been studied by EXAFS for some fluoride glasses in the system PbF₂M^II_tF₂M^III_tF₃ (M^II_t = Mn²⁺, Zn²⁺; M^III_t = Fe³⁺, Ga³⁺). Theoretical phase shifts and backscattering amplitude are used after testing with crystallized fluorides of various structures. Transition metals are sixfold coordinated and M_tF distances are very close to those known in crystallized compounds. Lead has eight to nine fluorine neighbors forming a very distorted polyhedra. Radial distributions, partially corrected for phase shifts, show a very weak second peak but the second neighbors nature and the distances cannot be determined without ambiguity.     

Binding and L23MM auger energies in atomic and metallic zinc

An analysis of the photoelectron and photon-induced L₂₃MM Auger spectra of Zn metal has been performed. The relaxation processes involved in the Auger transitions have been investigated. They account well for the experimental Auger energies.