Showing papers on "Ionic bonding published in 1999"
TL;DR: The linear generalized equation described in this paper provides a further dimension to the prediction of lattice potential energies/enthalpies of ionic solids and can be utilized to predict and rationalize the thermochemistry in topical areas of synthetic inorganic chemistry as well as in emerging areas.
Abstract: The linear generalized equation described in this paper provides a further dimension to the prediction of lattice potential energies/enthalpies of ionic solids. First, it offers an alternative (and often more direct) approach to the well-established Kapustinskii equation (whose capabilities have also recently been extended by our recent provision of an extended set of thermochemical radii). Second, it makes possible the acquisition of lattice energy estimates for salts which, up until now, except for simple 1:1 salts, could not be considered because of lack of crystal structure data. We have generalized Bartlett's correlation for MX (1:1) salts, between the lattice enthalpy and the inverse cube root of the molecular (formula unit) volume, such as to render it applicable across an extended range of ionic salts for the estimation of lattice potential energies. When new salts are synthesized, acquisition of full crystal structure data is not always possible and powder data provides only minimal structural in...
583 citations
Book•
01 Jan 1999
TL;DR: The basic approach bonding in tetrahedral semiconductors was proposed by as discussed by the authors, which is the basic approach for bonding in semiconductor materials. But it is not a complete approach to the analysis of semiconductor dielectric properties.
Abstract: The basic approach bonding in tetrahedral semiconductors elastic properties of semiconductors the dielectric properties of semiconductors semiconductor energy bands electronic properties effects of lattice distortions impurities and defects bonding in ionic crystals elastic properties of ionic crystals dielectric properties of ionic solids covalent insulators, SiO2 simple metals, electronic structure simple metals, bonding properties transition metals f-shell metals transition-metal (AB) compounds other transition and f-shell compounds surfaces and interfaces other systems.
522 citations
TL;DR: In this article, the energy of electrostatic attraction, transformation of ionic atmosphere and the hydration shell around a polyelectrolyte chain during the self-assembly were estimated on the basis of available theoretical and experimental data for aqueous polyethylte solutions.
304 citations
TL;DR: The superoxide radical anion O2- is both an important intermediate in heterogeneous catalytic oxidation and a useful probe for positive charges in ionic solids, such as metal oxides and zeolites as mentioned in this paper.
Abstract: The superoxide radical anion O2- is both an important intermediate in heterogeneous catalytic oxidation and a useful probe for positive charges in ionic solids, such as metal oxides and zeolites. The paper illustrates the main circumstances under which stable superoxide anions are formed at surfaces: (i) direct surface–oxygen electron transfer; (ii) photoinduced electron transfer; (iii) surface intermolecular electron transfer; (iv) decomposition of hydrogen peroxide.
303 citations
TL;DR: In this paper, the authors measured and interpreted the deposition of eight bacterial strains on Teflon and glass in aqueous media with ionic strengths varying between 0.0001 and 1 M. Two types of interactions were considered: van der Waals attraction and electrostatic repulsion (bacteria and surfaces are both negatively charged); and steric interactions between the outer cell surface macromolecules and the substrata.
260 citations
TL;DR: Hydrogen-ion titrations were conducted for hen-egg-white lysozyme in solutions of potassium chloride over the range pH 2.5−11.5 and for ionic strengths to 2.0 M, and the observed dependence of ion−protein interactions on pH and ionic strength is explained in terms of electric-double-layer theory.
Abstract: Hydrogen-ion titrations were conducted for hen-egg-white lysozyme in solutions of potassium chloride over the range pH 2.5−11.5 and for ionic strengths to 2.0 M. The dependence of lysozyme's net proton charge, zp, on pH and ionic strength in potassium chloride solution is measured. From the ionic-strength dependence of zp, interactions of lysozyme with potassium and chloride ions are calculated using the molecular- thermodynamic theory of Fraaije and Lyklema.1 Lysozyme interacts preferentially with up to 12 chloride ions at pH 2.5. The observed dependence of ion−protein interactions on pH and ionic strength is explained in terms of electric-double-layer theory. New experimental pKa data are reported for 11 amino acids in potassium chloride solutions of ionic strength to 3.0 M.
258 citations
TL;DR: In this article, the authors proposed a scaling approach, requiring no arbitrary parameters, for the analysis of the ac conductivity resulting from ionic motion in glasses, but this approach cannot be applied to alkali germanate glasses whose alkali content varies by more than a decade.
Abstract: In a recent Letter, Roling et al. [Phys. Rev. Lett. 78, 2160 (1997)] proposed a novel scaling approach, requiring no arbitrary parameters, for the analysis of the ac conductivity resulting from ionic motion in glasses. However, this approach cannot be applied to alkali germanate glasses whose alkali content varies by more than a decade, since changes which occur in the ion hopping length that accompany the changing alkali content are not incorporated. Here, I show that these changes can be incorporated into a universally valid approach which successfully scales the ac conductivity of sodium germanate glasses as well as two additional ionic systems without the introduction of arbitrary parameters.
252 citations
TL;DR: The relationship between charge and structure in restacked MS2 (M = Mo, W) has been probed by cation encapsulation and chemical oxidation and characterized by elemental analysis, electron diffracti... as discussed by the authors.
Abstract: The relationship between charge and structure in restacked MS2 (M = Mo, W) has been probed by cation encapsulation and chemical oxidation and characterized by elemental analysis, electron diffracti...
244 citations
IBM1
TL;DR: The authors showed that single-walled carbon nanotubes (SWNTs) can also be induced to organize themselves into rings or coils, with high yields of up to 50%. But unlike coils of biopolymers, in which hydrogen bonding and ionic interactions are usually involved, coils of SWNTs can be stabilized by van der Waals forces alone.
Abstract: Among the most studied processes of self-organization1, 2 are the coiling and ring formation of biopolymers such as DNA and proteins. These processes are complex, involving several different types of interaction. We have found that single-walled carbon nanotubes (SWNTs), which are renowned for their extremely high flexural rigidity3, 4, can also be induced to organize themselves into rings or coils, with high yields of up to 50%. But unlike coils of biopolymers, in which hydrogen bonding and ionic interactions are usually involved, coils of nanotubes can be stabilized by van der Waals forces alone.
241 citations
TL;DR: In this paper, an innovative approach has been used to probe the molecular nature of the metal oxide/aqueous solution interface using internal reflection spectroscopy of thin colloidal TiO2 films, under aqueous solutions of pH 11.7−2.3.
Abstract: An innovative approach has been used to probe the molecular nature of the metal oxide/aqueous solution interface. Internal reflection spectroscopy of thin colloidal TiO2 films, under aqueous solutions of pH 11.7−2.3, has been used to obtain differential in situ infrared spectra related to interfacial species. An alkaline solution wash of the TiO2 films was shown to remove contaminants arising from the sol evaporation−film deposition process. Specific infrared absorptions have been assigned to terminal Ti−OH and Ti−OH2+, adsorbed water Ti−OH2, and bridging Ti−OH+−Ti species from the pH dependence of spectra and from deuteration experiments. These surface species determine the pH-dependent surface charge and the enhanced interfacial ionic concentrations observed in our previously published STIRS results. The enhanced interfacial ionic concentrations were also observed to have spectral effects related to interfacial water structure which are similar to those observed from concentrated aqueous solutions conta...
232 citations
TL;DR: The selective catalytic reduction (SCR) of NO (2000 ppm) by NH3(2000 ppm), in the presence of oxygen (3%) was carried out on Cu(x)-FAU (x=theoretical exchange degree) catalysts prepared by ion exchange or impregnation and calcined at 773 K as discussed by the authors.
TL;DR: The structure and internal dynamics of β-lactoglobulin aggregates formed after heat-induced denaturation at pH 2 and different ionic strengths were investigated using light, neutron, and X-ray scattering as discussed by the authors.
Abstract: The structure and internal dynamics of β-lactoglobulin aggregates formed after heat-induced denaturation at pH 2 and different ionic strengths were investigated using light, neutron, and X-ray scattering. Polydisperse aggregates are formed with a rigid rodlike local structure with mass per unit length close to that of a string of β-lactoglobulin monomers but with a somewhat larger diameter. The persistence length decreases with increasing ionic strength from more than 600 nm at 0.013 M to 38 nm at 0.1 M. At ionic strengths of 0.1 and 0.2 M, a self-similar structure with fractal dimensions of 1.8 and 2.0 is seen by using light scattering. The concentration dependence of the static structure factor and the internal dynamics are close to those of flexible linear chains. In contrast, a rigid behavior is observed at lower ionic strength (0.03 and 0.013 M). The persistence length of aggregates formed at 0.013 M is reduced after dilution in 0.1 and 0.2 M ionic strength solvents but remains larger than that of ag...
TL;DR: The ionic contributions to the electrical conductivity are based on a differential effective medium approach and the influence of the temperature and the presence of a second immiscible and nonwetting phase is also considered in this model.
TL;DR: In this paper, the photoemission core-level spectra are analyzed in terms of a simple cluster model leading to estimates for the charge-transfer energy, the Coulomb correlation energy, and the hybridization strength V. This trend is attributed mostly to the increasing number of empty d states in the early transition metals which enhances the effective metal-ligand hybridization.
Abstract: We have performed photoemission and inverse photoemission experiments on a series of 3d-transition-metal oxides with formal ionic configuration from to . The photoemission core-level spectra are analysed in terms of a simple cluster model leading to estimates for the charge-transfer energy , the Coulomb correlation energy , and the hybridization strength V. It is found that the ratio of the correlation energy to the hybridization energy significantly decreases from the late to the early transition metal oxides. This trend is attributed mostly to the increasing number of empty d states in the early transition metals which enhances the effective metal-ligand hybridization. We also compare the experimental valence band spectra with densities of states (DOS) from band-structure calculations. The rather good agreement between the theoretical DOS and the measured single-particle excitation spectra of the early 3d-transition-metal oxides as opposed to the failure of the one-electron description for most of the late transition metal oxides supports the results of the cluster model analysis.
TL;DR: The structures of the new Ca(2+)-form and isomorphous structures of oligonucleotides with sequences GGCGAATTCGCG and GCGAAT TCGCG were determined at a maximum resolution of 1.3 A and revealed the most detailed picture yet of the ionic environment of B-DNA.
TL;DR: In this paper, the first time the published data on the synthesis and properties of donor-acceptor type of compounds based on fullerenes, various solvates and clathrates, inclusion compounds, molecular complexes and charge transfer complexes both with inorganic donors and with organoelement donors of the tetrathiafulvalene, amine, metallocene and metalloporphyrin series are discussed.
Abstract: The review generalises for the first time the published data on the synthesis and properties of donor-acceptor type of compounds based on fullerenes, various solvates and clathrates, inclusion compounds, molecular complexes and charge-transfer complexes both with inorganic donors and with organoelement donors of the tetrathiafulvalene, amine, metallocene and metalloporphyrin series. Radical ionic salts of fullerenes with bulky cations and alkali metals obtained by intercalation or by direct synthesis in solution are discussed. Results of studies of fullerene compounds by IR, optical, ESR, X-ray photoelectron and 13C NMR spectroscopy, as well as their conducting (including superconducting), magnetic and optical properties are discussed. The bibliography includes 208 references.
TL;DR: In this paper, the authors reported the first measurements of the composition and molecular orientation at the surface of a room-temperature ionic liquid 1-butyl-3methylimidazolium hexafluorophosphate.
Abstract: We report the first measurements of the composition and molecular orientation at the surface of a room-temperature ionic liquid1-butyl-3-methylimidazolium hexafluorophosphate, [bmim][PF6]. Recoil spectrometry using rare gas ions on continuously refreshed liquid surfaces in vacuo shows that neither ion is significantly enriched in the surface. The average orientation of the cation is with the plane of the ring vertical. The cation ring is rotated about an axis through its center such that the nitrogen atoms and side chains are deeper in the surface with the surface normal passing between the two nitrogen atoms (with an estimated error of ±30°).
TL;DR: In this article, a design strategy to obtain organic-organometallic crystals by means of a selective use of strong hydrogen bonds between the organic component and of weak hydrogen bond between organic and organometallic components is illustrated with emphasis on the role of charge-assisted C-Hδ+⋯Oδ− hydrogen bonds.
TL;DR: In this article, a simple mathematical model for calculating the chemical activity coefficients of ions in electrolytic solutions is presented to account for the particular behavior of concentrated solutions for which short-range and long-range interactions between ions are important.
TL;DR: In this paper, the synthesis of novel neutral rare-gas-containing molecules of type HXY, where × = Xe or Kr and Y is an electronegative atom or fragment, is discussed.
Abstract: The synthesis of novel neutral rare-gas-containing molecules of type HXY, where × = Xe or Kr and Y is an electronegative atom or fragment, is discussed. The molecules are characterised experimentally by their vibrational spectra and computationally by extensive ab initio calculations. They are formed in low-temperature rare-gas solids from neutral reagents and their bonding consists of both covalent and ionic contributions. Our recent studies add to the previously known class of rare-gas chemical bonds in neutral ground-state molecules the new bonds Xe–H, Xe–I, Xe–Br, Xe–S, Kr–H, Kr–C, and Kr–Cl.
TL;DR: In this paper, a single crystal of hexagonal apatite type Nd 9·33 (SiO 4 ) 6 O 2 which is an oxide ionic conductor was prepared by the FZ method and an anisotropy of its conductivity was investigated.
Abstract: Single crystal of hexagonal apatite type Nd 9·33 (SiO 4 ) 6 O 2 which is an oxide ionic conductor was prepared by the FZ method and an anisotropy of its conductivity was investigated. The conductivity of a parallel component to a c-axis (2·1×10 −8 S cm −1 at 30°C) was higher about one order of magnitude, compared with that of perpendicular component.
TL;DR: In this article, a review of the NMR investigations of graphite fluorides and fluorine-graphite intercalation compounds is presented, where the origin of semimetal metal and metal-insulator transformations, localization effects and C-F bonding in fluorine graphite intercation compounds are discussed.
TL;DR: In this paper, the electronic energy band structure, site and angular momentum decomposed density of states (DOS), and charge-density contours for ferroelectric sodium nitrite have been calculated using an accurate full-potential linear muffin-tin orbital method.
Abstract: The electronic-energy band structure, site and angular momentum decomposed density of states (DOS), and charge-density contours for ferroelectric sodium nitrite have been calculated using an accurate full-potential linear muffin-tin orbital method. The calculated total DOS is found to be in good agreement with experimental x-ray-photoemission spectra. From the DOS analysis, as well as charge-density studies, we conclude that the bonding between Na and ${\mathrm{NO}}_{2}$ is ionic and that the ${\mathrm{NO}}_{2}$ entities bond covalently. The polarized reflectivity spectra, calculated in a large energy range up to 30 eV, are directly compared with recent experimental spectra. The optical anisotropy in this material is analyzed through the optical functions such as refractive indices and static dielectric constants along the principal axes. Our calculated band structure and optical spectra are also compared with results obtained from the orthogonalized linear combination of atomic orbital method. The role of antiferroelectric distortion on the optical property and structural stability is discussed.
TL;DR: In this paper, the authors describe ionic conductivities in the 7 × 10-5 to 7× 10-10 Ω-1 cm-1 range, which permit microelectrode voltammetry in the undiluted materials, examples of which are presented.
Abstract: Interesting ionic materials can be transformed into room temperature molten salts by combining them with polyether-tailed counterions such as polyether-tailed 2-sulfobenzoate (MePEG-BzSO3-) and polyether-tailed triethylammonium (MePEG-Et3N+). Melts containing ruthenium hexamine, metal trisbipyridines, metal trisphenanthrolines, and ionic forms of aluminum quinolate, anthraquinone, phthalocyanine, and porphyrins are described. These melts exhibit ionic conductivities in the 7 × 10-5 to 7 × 10-10 Ω-1 cm-1 range, which permit microelectrode voltammetry in the undiluted materials, examples of which are presented.
TL;DR: In this paper, the interaction of primary water dissociation products H, O and OH with various (111) metal surfaces is studied by density functional theory (DFT) calculations using clusters.
TL;DR: In this article, a new interpretation of Reff implies that the correct expression for the solvation free energy is a combination of two Born free energies, which incorporate the effects of dielectric saturation and electrostricti...
Abstract: The Born model of ionic solvation prescribes the solvation free energy of ions in a dielectric continuum and is widely used. Despite the fact that the solvent molecules around the ions are highly structured giving rise to molecular phenomena such as dielectric saturation and electrostriction, the Born model yields accurate results compared to experimental data if a proper radius for the ion, the effective Born radius, Reff, is chosen. On the basis of molecular dynamics simulations of ions of varying charge and size in TIP3P water, Reff is identified as the mean of the ionic radius (Rion) and the first peak position in the ion−water pair distribution function (Rgmax). This relationship was verified using experimentally available Rgmax for ions of varying size (0.4−3.0 A) and charge (−3e to +4e). The new interpretation of Reff implies that the correct expression for the solvation free energy is a combination of two Born free energies, which incorporate the effects of dielectric saturation and electrostricti...
TL;DR: In this article, an exhaustive collection of dielectric relaxation data of glassy, crystalline, and molten ionic conductors are analyzed to obtain the magnitudes of their constant losses and the dependencies on temperature, ion density, ion mass, dc conductivity activation energy, dcconductivity level, the nonexponential conductivity relaxation parameter β, the mixed alkali effect, and the decoupling index Rτ.
Abstract: A frequency independent or nearly frequency independent contribution to the dielectric loss is present in all ionic conductors independent of the chemical and physical structures. An exhaustive collection of dielectric relaxation data of glassy, crystalline, and molten ionic conductors are analyzed to obtain the magnitudes of their constant losses and the dependencies on temperature, ion density, ion mass, dc conductivity activation energy, dc conductivity level, the nonexponential conductivity relaxation parameter β, the mixed alkali effect, and the decoupling index Rτ. Trends of changes in the constant loss when modifying the structure of the glassy matrix or mixing two different alkali ions are also found. In a glass-forming molten salt, 0.4Ca(NO3)2⋅0.6KNO3, the constant loss turns out to have approximately the same temperature dependence as the mean square displacement of the ions obtained by elastic neutron scattering measurement. All dependencies and properties found indicate that the physical origin of the constant loss may be traced to the displacement of the ions in their local librational or vibrational motion, but anharmonicity is not a necessary ingredient.
TL;DR: In this paper, a review of experimental data for the adsorption of divalent metal ions (M{sup 2+}) onto oxide and hydroxide surfaces from solutions of strong electrolytes has typically been inferred to take place without the involvement of the electrolyte anion.
Abstract: Adsorption of divalent metal ions (M{sup 2+}) onto oxide and hydroxide surfaces from solutions of strong electrolytes has typically been inferred to take place without the involvement of the electrolyte anion. Only in situations where M{sup 2+} forms a strong enough aqueous complex with the electrolyte anion (for example, CdCl{sup +} or PbCl{sup +}) has it been frequently suggested that the metal and the electrolyte anion adsorb simultaneously. A review of experimental data for the adsorption of Cd{sup 2+}, Pb{sup 2+}, Co{sup 2+}, UO{sub 2}{sup 2+}, Zn{sup 2+}, Cu{sup 2+}, Ba{sup 2+}, Sr{sup 2+}, and Ca{sup 2+} onto quartz, silica, goethite, hydrous ferric oxide, corundum, {gamma}-alumina, anatase, birnessite, and magnetite, from NaNO{sub 3}, KNO{sub 3}, NaCl, and NaClO{sub 4} solutions over a wide range of ionic strengths (0.0001 M-1.0 M), reveals that transition and heavy metal adsorption behavior with ionic strength is a function of the type of electrolyte. In NaNO{sub 3} solutions, metal adsorption exhibits little or no dependence on the ionic strength of the solution. However, in NaCl solutions, transition and heavy metal adsorption decreases strongly with increasing ionic strength. In NaClO{sub 4} solutions, metal adsorption decreases strongly with increasing ionic strength. In NaClO{sub 4} solutions, metal adsorptionmore » exhibits little dependence on ionic strength but is often suggestive of an increase in metal adsorption with increasing ionic strength. Analysis of selected adsorption edges was carried out using the extended triple-layer model and aqueous speciation models that included metal-nitrate, metal-chloride, and metal-hydroxide complexes.« less
TL;DR: In this paper, the authors investigated the variation of the ionic conductivity as a function of the composition x is investigated in the temperature range 150-600 K. They showed that the variations of ionic motion process in the bulk of the material can be explained by structural considerations, and that the mobility of the Na+ ions in these materials seems to be mostly influenced by the size of the bottlenecks through which the ions have to pass.
TL;DR: In this paper, a detailed vibrational spectroscopic study of the ionic species present in the (PEO)xLiTf system (x = 3−100) indicates that free ions and ion pairs are the dominant species in the dilute salt region at room temperature.
Abstract: A detailed vibrational spectroscopic study of the ionic species present in the (PEO)xLiTf system (x = 3−100) indicates that “free” ions and ion pairs are the dominant species present in the dilute salt region at room temperature. When the salt concentration is increased to an O:M ratio of about 40:1, a band due to an aggregate species first appears and is assigned to the triflate ion vibrating in the (PEO)3LiCF3SO3 compound. The amorphous phase of (PEO)3LiCF3SO3 was studied by examining the temperature dependence of the spectra as the compound was heated through the melting transition at about 176 °C. Spectral behavior of the CH2 rocking modes and the COC stretching mode indicated that disordering above the melting temperature resulted in a broad distribution of −O−C−C−O− torsional angles. However the basic lithium-polyether backbone interaction was not been significantly changed for at least 15 °C above the transition temperature. Additional effects of thermal disordering were noted in the CF3 symmetric ...