Ionic Configurations Research Articles

\u03b1-Thio Carbocations (Thionium Ions) as Intermediates in Br\xf8nsted Acid-Catalyzed Reactions of Enone-Derived 1,3-Dithianes and 1,3-Dithiolanes

Evidence was collected for the intermediate formation of thionium ions in Brønsted acid-catalyzed [2 + 2] photocycloaddition and electrophilic addition reactions to enone dithianes and dithiolanes. Low-temperature NMR studies helped to elucidate the structure and configuration of the thionium ions and thus support previous and current results obtained by UV/Vis spectroscopy.Graphical

The Crystal Structure and Magnetic Behavior of Quinary Osmate and Ruthenate Double Perovskites La ABB'O6 ( A = Ca, Sr; B = Co, Ni; B' = Ru, Os).

Six La ABB'O6 ( A = Ca, Sr; B = Co, Ni; B' = Ru, Os) double perovskites were synthesized, several for the first time, and their crystal structures and magnetic behavior were characterized with neutron powder diffraction and direct-current and alternating-current magnetometry. All six compounds crystallize with P21 /n space group symmetry, resulting from a- a- c+ octahedral tilting and complete rock salt ordering of transition-metal ions. Despite the electronic configurations of the transition-metal ions, either d8-d3 or d7-d3, not one of the six compounds shows ferromagnetism as predicted by the Goodenough-Kanamori rules. LaSrNiOsO6, LaSrNiRuO6, and LaCaNiRuO6 display long-range antiferromagnetic order, while LaCaNiOsO6, LaCaCoOsO6, and LaSrCoOsO6 exhibit spin-glass behavior. These compounds are compared to the previously studied LaCaCoRuO6 and LaSrCoRuO6, both of which order antiferromagnetically. The observed variations in magnetic properties can be attributed largely to the response of competing superexchange pathways due to changes in B-O- B' bond angles, differences in the radial extent of the 4d ( B' = Ru) and 5d ( B' = Os) orbitals, and filling of the t2g orbitals of the 3d ion.

Average Intermolecular Distances and Dynamics of Ruthenium-Containing Organometallic Ionic Liquids Studied by Nuclear Overhauser Effects between 19F and 1H Nuclei and NMR Relaxation Rate Measurements

Abstract The physical properties of organometallic ionic liquids containing cationic ruthenium sandwich complexes {[Ru(C5H5)(C6H5R)]X; R = OCH(C4H9)2, OCH(C2H5)(C6H13); X = N(SO2CF3)2, N(SO2F)2} are dependent on the substituents. To obtain detailed information about the motional states and configurations of the constituent ions of these ionic liquids, we performed one-dimensional (1D) heteronuclear Overhauser enhancement spectroscopy (HOESY) NMR experiments and the standard relaxation rate (1/T1 and 1/T2) measurements. We determined the intermolecular cross-relaxation rates between some cation blocks and the anion in each ionic liquid by analyzing the experimental data based on the extended Solomon differential equations. As a result, we were able to estimate several intermolecular distances between the cations and anions in the ionic liquids. This is the first time that NMR has been applied to the determination of the intermolecular cross-relaxation rates and the estimation of intermolecular distances of highly viscous ionic liquids consisting of heteronuclear multiple-spin systems without the support of any X-ray data. The viscosities of these ionic liquids depended largely on the motional correlation times of the cations rather than on the intermolecular distances between the cations and anions.

Bond-length distributions for ions bonded to oxygen: results for the lanthanides and actinides and discussion of the f-block contraction

Bond-length distributions have been examined for 84 configurations of the lanthanide ions and 22 configurations of the actinide ions bonded to oxygen, for 1317 coordination polyhedra and 10 700 bond distances for the lanthanide ions, and 671 coordination polyhedra and 4754 bond distances for the actinide ions. A linear correlation between mean bond length and coordination number is observed for the trivalent lanthanides ions bonded to O2−. The lanthanide contraction for the trivalent lanthanide ions bonded to O2− is shown to vary as a function of coordination number, and to diminish in scale with an increasing coordination number. The decrease in mean bond length from La3+ to Lu3+ is 0.25 Å for coordination number (CN) 6 (9.8%), 0.22 Å for CN 7 (8.7%), 0.21 Å for CN 8 (8.0%), 0.21 Å for CN 9 (8.2%) and 0.18 Å for CN 10 (6.9%). The crystal chemistry of Np5+ and Np6+ is shown to be very similar to that of U6+ when bonded to O2−, but differs for Np7+.

Bond-length distributions for ions bonded to oxygen: metalloids and post-transition metals

Bond-length distributions have been examined for 33 configurations of the metalloid ions and 56 configurations of the post-transition metal ions bonded to oxygen, for 5279 coordination polyhedra and 21 761 bond distances for the metalloid ions, and 1821 coordination polyhedra and 10 723 bond distances for the post-transition metal ions. For the metalloid and post-transition elements with lone-pair electrons, the more common oxidation state between n versus n+2 is n for Sn, Te, Tl, Pb and Bi and n+2 for As and Sb. There is no correlation between bond-valence sum and coordination number for cations with stereoactive lone-pair electrons when including secondary bonds, and both intermediate states of lone-pair stereoactivity and inert lone pairs may occur for any coordination number > [4]. Variations in mean bond length are ∼0.06–0.09 Å for strongly bonded oxyanions of metalloid and post-transition metal ions, and ∼0.1–0.3 Å for ions showing lone-pair stereoactivity. Bond-length distortion is confirmed to be a leading cause of variation in mean bond lengths for ions with stereoactive lone-pair electrons. For strongly bonded cations (i.e. oxyanions), the causes of mean bond-length variation are unclear; the most plausible cause of mean bond-length variation for these ions is the effect of structure type, i.e. stress resulting from the inability of a structure to adopt its characteristic a priori bond lengths.

Relativistic all-order many-body calculation of energies, wavelengths, and M1 and E2 transition rates for the 3d n configurations in tungsten ions.

Energy levels, wavelengths, magnetic-dipole and electric-quadrupole transition rates between the low-lying states are evaluated for W51+ to W54+ ions with 3d n (n = 2 to 5) electronic configurations by using an approach combining configuration interaction with the linearized coupled-cluster single-double method. The QED corrections are directly incorporated into the calculations and their effect is studied in detail. Uncertainties of the calculations are discussed. This study of such highly charged ions with the present method opens the way for future applications allowing an accurate prediction of properties for a very wide range of highly charged ions aimed at providing precision benchmarks for various applications.

Directly calculated electrical conductivity of hot dense hydrogen from molecular dynamics simulation beyond Kubo-Greenwood formula

Electrical conductivity of hot dense hydrogen is directly calculated by molecular dynamics simulation with a reduced electron force field method, in which the electrons are represented as Gaussian wave packets with fixed sizes. Here, the temperature is higher than electron Fermi temperature (T>300 eV, ρ=40 g/cc). The present method can avoid the Coulomb catastrophe and give the limit of electrical conductivity based on the Coulomb interaction. We investigate the effect of ion-electron coupled movements, which is lost in the static method such as density functional theory based Kubo-Greenwood framework. It is found that the ionic dynamics, which contributes to the dynamical electrical microfield and electron-ion collisions, will reduce the conductivity significantly compared with the fixed ion configuration calculations.

Exploring non-linearities of carbon-based microsupercapacitors from an equivalent circuit perspective

Besides accurate capacitance determination, an equivalent-circuit analysis reveals the ion configurations of microsupercapacitors that lead to non-linear electronic behaviors of these miniature energy-storage devices.

Gehlenite and anorthite formation from fluid fly ash

Fluid fly ash could be considered a waste, but, when well treated, it may also become a useful secondary source material. Its rather high content of calcium-containing phases along with thermally treated alumino-silicate residues resulting from coal combustion can lead to the formation of a stable system with newly formatted phases. The high temperature destroys the clay lattice and activates a new configuration of aluminum ions, changing their coordination to oxygen. The effect is accompanied by changes in charge in the surroundings, which are compensated for by calcium ions. The higher the temperature of the fluid ash treatment, the more pronounced the appearance of gehlenite and anorthite in the final mass. Both are natural materials and, together with mullite and anhydrite, they could ensure safety and protection even if exposed to open fire of up to 1150 °C.

Ground-state configurations and theoretical soft-x-ray emission of highly charged actinide ions

It is well known that the lanthanide and actinide elements are formed by the filling of $4f$ and $5f$ subshells which occurs after the filling of $5d$ and $6d$ subshells, respectively, has begun. With increasing ionization one expects the energy levels to eventually regroup to their hydrogenic ordering, i.e., in terms of principal quantum number. In the lanthanides, the $4f$ electron binding energy overtakes that of $5p$ near the 6th or 7th ion stage and $5s$ near the 14th or 15th ion stage, leading to dramatic rearrangements of ground-state configurations. In this paper we report on the results of a study to explore the effects of increasing ionization on the ground-state configurations of actinide ions as a result of $5f$ and $6p$ or $6s$ level crossings. It is seen that the effects generally occur later and are more strongly influenced by spin-orbit splitting than in the lanthanides. The near degeneracies of $5f$ and $6l$ energies in these stages lead to configuration interaction (CI) amongst configurations with variable numbers of $5f$ and $6p$ electrons. The effects of CI on the level complexity are explored for ions along the Rn I sequence and are found to lead to the formation of ``compound states'' as predicted for the lanthanides. The extreme ultraviolet and soft x-ray spectra of medium and highly charged lanthanides are dominated by emission from unresolved transition arrays (UTAs) of the type $\mathrm{\ensuremath{\Delta}}n=0$, $4{p}^{6}4{d}^{N+1}\ensuremath{-}4{p}^{5}4{d}^{N+2}+4{p}^{6}4{d}^{N}4f$, which, in general, overlap in adjacent ion stages of a particular element. Here, the corresponding $\mathrm{\ensuremath{\Delta}}n=0$, $5{p}^{6}5{d}^{N+1}\ensuremath{-}5{p}^{5}5{d}^{N+2}+5{p}^{6}5{d}^{N}5f$ UTAs have been studied theoretically with the aid of Hartree-Fock with configuration interaction calculations. As well as predicting the wavelengths and spectral details of the anticipated features, the calculations show that the effects of configuration interaction are quite different for the two different families of $\mathrm{\ensuremath{\Delta}}n=0$ transitions and, once more, spin-orbit interactions play a major role.

Mean bond-length variations in crystals for ions bonded to oxygen

Variations in mean bond length are examined in oxide and oxysalt crystals for 55 cation configurations bonded to O2−. Stepwise multiple regression analysis shows that mean bond length is correlated to bond-length distortion in 42 ion configurations at the 95% confidence level, with a mean coefficient of determination (〈R 2〉) of 0.35. Previously published correlations between mean bond length and mean coordination number of the bonded anions are found not to be of general applicability to inorganic oxide and oxysalt structures. For two of 11 ions tested for the 95% confidence level, mean bond lengths predicted using a fixed radius for O2− are significantly more accurate as those predicted using an O2− radius dependent on coordination number, and are statistically identical otherwise. As a result, the currently accepted ionic radii for O2− in different coordinations are not justified by experimental data. Previously reported correlation between mean bond length and the mean electronegativity of the cations bonded to the oxygen atoms of the coordination polyhedron is shown to be statistically insignificant; similar results are obtained with regard to ionization energy. It is shown that a priori bond lengths calculated for many ion configurations in a single structure-type leads to a high correlation between a priori and observed mean bond lengths, but a priori bond lengths calculated for a single ion configuration in many different structure-types leads to negligible correlation between a priori and observed mean bond lengths. This indicates that structure type has a major effect on mean bond length, the magnitude of which goes beyond that of the other variables analyzed here.

Electronic-Structure Origin of Cation Disorder in Transition-Metal Oxides.

Cation disorder is an important design criterion for technologically relevant transition-metal (TM) oxides, such as radiation-tolerant ceramics and Li-ion battery electrodes. In this Letter, we use a combination of first-principles calculations, normal mode analysis, and band-structure arguments to pinpoint a specific electronic-structure effect that influences the stability of disordered phases. We find that the electronic configuration of a TM ion determines to what extent the structural energy is affected by site distortions. This mechanism explains the stability of disordered phases with large ionic radius differences and provides a concrete guideline for the discovery of novel disordered compositions.

(FeIn2S4) x · (AgIn5S8)1–x alloys: Crystal structure, nuclear γ-Resonance spectra, and band gap

FeIn2S4) x · (AgIn5S8)1–x alloy single crystals are grown in the entire region of composition parameters x by the Bridgman method. It is established that the single crystals crystallize in the cubic spinel structure. Nuclear γ-resonance spectroscopy is used to study the local configurations of iron ions in the structure of (FeIn2S4) x · (AgIn5S8)1–x alloys. From the transmittance spectra in the region of the fundamental absorption edge, the band gap (E g) of the alloys is determined, and its concentration dependence is constructed. It is shown that E g nonlinearly varies with x.

Self-Organization of Ions at the Interface between Graphene and Ionic Liquid DEME-TFSI.

Electrochemical effects manifest as nonlinear responses to an applied electric field in electrochemical devices, and are linked intimately to the molecular orientation of ions in the electric double layer (EDL). Herein, we probe the origin of the electrochemical effect using a double-gate graphene field effect transistor (GFET) of ionic liquid N,N-diethyl-N-(2-methoxyethyl)-N-methylammonium bis(trifluoromethylsulfonyl)imide (DEME-TFSI) top-gate, paired with a ferroelectric Pb0.92La0.08Zr0.52Ti0.48O3 (PLZT) back-gate of compatible gating efficiency. The orientation of the interfacial molecular ions can be extracted by measuring the GFET Dirac point shift, and their dynamic response to ultraviolet-visible light and a gate electric field was quantified. We have observed that the strong electrochemical effect is due to the TFSI anions self-organizing on a treated GFET surface. Moreover, a reversible order-disorder transition of TFSI anions self-organized on the GFET surface can be triggered by illuminating the interface with ultraviolet-visible light, revealing that it is a useful method to control the surface ion configuration and the overall performance of the device.

Probing Self-Organization of Molecular Ions at the Interface between Graphene and Ionic Liquids

Electrochemical effect manifests itself as an unfavorable nonlinear response to an applied electric field in electrochemical devices and links intimately to the configuration of the molecular ions in the electric double layer (EDL) formed at the electrolyte/electrode interface. In this work, we probe the origin of the electrochemical effect using a double-gate graphene field effect transistor (GFET) of ionic liquid DEME-TFSI (or BMP-TFSI) top-gate, paired with ferroelectric Pb0.92La0.08Zr0.52Ti0.48O3 (PLZT) back-gate of compatible gating efficiency. By measuing the GFET Dirac point shift in response to the bi-polar charge doping of the EDL molecular ions, the configurations of the interface molecular ions can be extracted and their dynamic response to visible light and gate electric field, quantified. We have observed that a strong electrochemical effect sets in as a consequence of the TFSI molecular anions self-organizing on a treated GFET surface, resulting in the Dirac point shift to a large positive voltage. Moreover, a reversible order-disorder transition of this molecular ion monolayer can be triggered using light illumination, revealing the critical role of the surface ion configuration on the overall performance of electrochemical devices.

Universal Design Strategy for Li Super-Ionic Conductors in All-Solid-State Li-Ion Batteries : A First-Principles Study

Lithium super-ionic conductor (SIC) materials are the key component in enabling all solid-state Li-ion batteries. However, it has not yet been understood why only a few materials as super-ionic conductors can achieve exceptionally higher ionic conductivity than typical solids and how one can design fast ion conductors following simple principles. Using ab initio modeling, we show that fast diffusion in super-ionic conductors happens through unique concerted migration mechanism of multiple ions with low energy barrier in contrast to typical solids. We elucidate that low energy barriers of the concerted ionic diffusion are a result of unique mobile ion configurations and strong mobile ion interactions in super-ionic conductor materials, such as Li10GeP2S12, lithium garnet, NASICON, etc. Our theory provides a conceptually simple framework for guiding the design of super-ionic conductor materials. We demonstrate this strategy by designing a number of novel fast ion conducting materials to activate concerted migration with reduced diffusion barrier. The novel materials are predicted to have comparable Li+ ionic conductivity at room temperature to the known Li SIC materials. In summary, our proposed theory and identified mechanism are universally for fast diffusion in a broad range of ionic conducting materials, and provide a general framework and a universal strategy to design solid materials with fast ionic diffusion.

Metal Effects on the Sensitivity of Isostructural Metal-Organic Frameworks Based on 5-Amino-3-nitro-1H-1,2,4-triazole.

Two energetic metal-organic frameworks (MOFs), Co-ANTA and Zn-ANTA, are synthesized from 5-amino-3-nitro-1H-1,2,4-triazole (ANTA) and exhibit superior oxygen balance, density, and thermal stability compared to ANTA. The superior oxygen balance is achieved through a combination of hydroxide ligands and deprotonated linkers. Although the materials are isostructural and have similar density, oxygen balance, and sensitivity to heat, their impact sensitivities are significantly different. Similar to ANTA, Zn-ANTA is fairly insensitive to impact. By contrast, the impact sensitivity of ANTA is increased significantly after coordination polymerization with cobalt. The disparate impact sensitivities of the compounds might be attributed to the different electronic configurations of the metal ions constituting the frameworks.

Influence of alkaline ions on the luminescent properties of Mn4+-doped MGe4O9 (M = Li2, LiNa and K2) red-emitting phosphors

Mn4+ -doped MGe4O9 (M = Li2, LiNa and K2) red-emitting phosphors were successfully prepared and characterized. Owing to the different ionic radii and electron configurations among the Li, Na and K ions, the MGe4O9 (M = Li2, LiNa and K2) compounds have different space group and crystal structure, such as different bond lengths, bond angles, crystal fields and nephelauxetic effect. Under the excitation of ultraviolet and blue light, the studied samples emit visible red emissions. The thermal stabilities of phosphors are greatly affected by the alkaline ions, especially when M = LiNa and K2, the thermal stability is significantly enhanced. Furthermore, the crystal field strength (Dq) and Racah parameters (B and C) are estimated to evaluate the nephelauxetic effect of Mn4+ ions in MGe4O9 (M = Li2, LiNa and K2) host lattices. The results indicate that the alkaline ions can influence the red emissions of Mn4+ ions in MGe4O9 (M = Li2, LiNa and K2) phosphors and these resultant phosphors may have potential applications for solid state lighting.

Structural, magnetic, electrical and electrochemical properties of SrCoO2.5, Sr9Co2Mn5O21 and SrMnO3 compounds

SrCo1−xMnxO3−d (0 ≤ x ≤ 1) were synthesized by conventional solid state reaction method. We found that Mn substitution hinders the decomposition of carbonate at 900 °C and increases the synthesis temperature of SrCo1−xMnxO3−d to 1200 °C. Three different main phases emerge as the Mn content is increased; SrCoO2.5, Sr9Co2Mn5O21 and SrMnO3. Structural properties of the samples were investigated by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, x-ray diffraction (XRD) and scanning electron microscopy (SEM). Valance states of the transition metal (TM) ions were estimated based on lattice parameters and ionic radii of TM ions. High temperature resistivity measurements show hysteresis upon heating and cooling and is attributed to oxygen release without any endothermic/exothermic activity. The spin configurations of Co and Mn ions in SrCoO2.5, Sr9Co2Mn5O21 and SrMnO3 were estimated by Curie-Weiss fitting of χ-T curves. Electrochemical measurements show two anodic/cathodic peaks indicating two main types of oxygen sites in the unit cell.

Magnetic and magnetoresistance properties of La0.7Sr0.3(Mn,Сo)O3

Magnetic and magnetotransport properties of La0.7Sr0.3Mn1−xCoxO3 ceramics have been investigated by neutron powder diffraction, magnetization and electrical measurements. It is shown that substitution by cobalt ions leads to a decrease of magnetic transition temperature down to 140K for the compound with x = 0.33. The compounds with cobalt content 0.4 < x < 0.6 are characterized by a presence of small ferromagnetic component due to exchange interactions between cobalt and manganese ions with maximal transition temperature of about 190K observed for x = 0.5. Further increase of the dopant concentration diminishes ferromagnetic interactions. An evolution of electronic configuration of manganese and cobalt ions upon chemical substitution as well as related changes in the exchange interactions which determine the type of the magnetic state are discussed. Based on the neutron diffraction results and magnetometry data the preliminary magnetic phase diagram has been constructed.