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The Mossbauer emission spectrum of 57Co in CoFe2O4 is reported. Electron capture leads to the formation of 57Fe3+ substituting 57Co2+. The stabilization of the aliovalent charge state is consistent with an electrostatic model. Le spectre d'emission de 57Co dans CoFe2O4 indique que la capture electronique conduit a la formation de 57Fe3+ en substitution de 57Co2+. La stabilisation de l'etat de charge aliovalent est expliquee selon un modele electrostatique.

The shift and the change in intensity of the OH stretching bands of decationated near-faujasite (Y) zeolites have been studied with respect to the physical adsorption of N2, O2, CH4, Ar and Kr. The high-frequency OH stretching was assigned to hydroxyls in the supercage and the low-frequency OH stretching to hydroxyls in the cubo-octahedron. A simple electrostatic model allows one to correlate the shift and the change in intensity of the high-frequency OH band to the dielectric constant of adsorbed species. The reaction field of the OH dipole in an ellipsoidal cavity surrounded by the adsorbed molecules seems to be responsible for the perturbation undergone by the OH oscillator when the dielectric constant around the cavity is modified.

The frequencies and intensities of the fundamental and some overtones of v (CH) of n-propyl acetylene have been measured in a number of different solvents. Mechanical anharmonicity terms have been calculated and a quantitative prediction of the intensity values has been attempted by using a simple electrostatic model which quantitatively represents the frequency changes.

A study was made of the relative effectiveness of four work trip distribution methods as applied to a rapidly growing industrial complex in and near Lexington, Kentucky. The distribution procedures tested were the Electrostatic Model, Gravity Model, Competing Opportunities Model, and Multiple Regression Model. Each was evaluated by comparing the distributions computed from the model with the actual interchange of industrial work trips obtained from a large-sample origin and destination (O and D) survey. The Multiple Regression Model, derived from the O and D data, yielded the most accurate distribution patterns. Of the three theoretical procedures, the Gravity Model proved most effective.

Free energy and enthalpy of single ion solvation in water and propylene carbonate, using electrostatic model

The authors show that the crystalline potential of erbium gallium garnet, obtained from the analysis of the optical absorption spectrum, can be explained using a simple electrostatic model. They thus determine the values of the leading terms of the potential, as well as an estimation of the average values 〈 r 4 〉 and 〈 r 6 〉 which they compare with the existing theoretical calculations.

A simple electrostatic model has been used to demonstrate that the inner surface hydroxyls in kaolinite, dickite and nacrite are responsible for the interlayer bonding in these minerals. The contribution to the interlayer bonding of an individual hydroxyl hydrogen depends on the orientation of the hydroxyl group relative to the 1: 1 layer since this orientation determines the H—O interlayer distance. If this distance is much greater than the sum of the van der Waals radii, 2·60 A, there is essentially no bond. As the distance becomes less than 2·60 A, the strength of the interlayer bond increases.

With increasing temperature the infrared absorption bands of Mg(OH) 2 shift to lower wave numbers and the strong absorption maximum between 660–300 cm −1 shows a marked decrease in intensity. The unexpectedly large positive temperature shift of the OH-stretching band at 3700 cm −1 is related to the thermal expansion of the Mg(OH) 2 lattice, which is anisotropic having its largest value parallel to the mean OH-vector. The shift can be explained by an electrostatic model taking into account the next-to-nearest neighbours of the OH − -group. The true O—H bond distance probably increases beyond the value of 0·984 A extrapolated for Ca(OH) 2 at low temperatures.

The stabilities (as ΔG0f) of monatomic lanthanide anions in liquid ammonia are estimated from a simple electrostatic model. It is shown that the existence of lanthanide anions in this solvent is highly improbable.

Ion association at the surface of a micelle is reinterpreted by considering that counter ions are bound by an electrostatic attraction with a spherical shell which is formed by the aggregation of the polar heads of amphiphilic molecules. It was found that the degree of ion association increased slightly with the increase in the aggregation number of amphiphilic molecules.

Intensity data for transitions between the 4f 2 crystal-field levels of Pr 3+ in LiYF 4 are parameterized. The results are consistent with an electrostatic model for f-f electric dipole intensities which includes both static crystal-field effects and dynamic ligand-polarization effects. They are also consistent with the superposition model for lanthanide-ligand interactions in lanthanide compounds.

The stabilities (as ΔGfo) of monatomic actinide anions in liquid ammonia are estimated from a simple electrostatic model. It is shown that, with the possible exception of Md−, the existence of actinide anions in this solvent is highly improbable.

Both the N—N stretching vibration and its combination with the Fermi doublet {ν 1 , 2 ν 2 } of carbon dioxide are infrared active for a nitrogen crystal containing traces of carbon dioxide. The intensities of these normally forbidden bands can be accounted for semiquantitatively by a simple electrostatic model.

A collection of 4 positive and 4 negative point charges arranged as two interpenetrating tetrahedra subject only to Coulombic forces has a minimum electrostatic energy at a ratio of the two tetrahedra sides of 0.783, a value consistent with the observed LiLi to CC distance ratio of 0.73 in the structure of methyllithium tetramer.

From the dependence of the molal osmotic coefficients of (hept) 4 NX ( X = Cl, Br, J), (hept) 4 NNO 3 and (oct) 4 PNO 3 , in benzene at 33, 40 and 50°C, on the solute concentration, the dimerization constants of solute ion-pairs and the corresponding thermodynamic functions of dimerization, ΔG °, ΔH ° and ΔS ° have been calculated. The thermodynamic data are discussed in terms of a simple electrostatic model of association.

The self-consistent unrestricted Hartree-Fock method was used to study the adsorption of argon on cluster models of ${\mathrm{Al}}_{2}$${\mathrm{O}}_{3}$ surfaces. We have considered surfaces parallel and perpendicular to the hexagonal $c$ axis and obtained a maximum binding of 0.5 eV, in good agreement with experiment. We propose a simple electrostatic model to account for this binding.

Relationships between crystal-field radial integrals which lead to an effective crystal-field hamiltonian of the same type as the one postulated in the Ξ2 approach are given in this letter. The angular overlap model in its Ξ2 restriction then appears as a particular case of the electrostatic model.

For the aromatic molecules benzene, naphthalene, and anthracene a relation is found between dipole moment and dissociation constant of the hydroxy compounds and the carboxylic acids on the one hand and theπ-electron density at the respective carbon atom in the unsubstituted molecule on the other hand. The following statement can be made:—Theπ-electron density at a carbon atom of these aromatic systems is found to increase with its positive character. The effect is explained by using an electrostatic model.

The H coordinates are given for eight hydrated manganese chlorides, all of which become antiferro‐magnetic at low temperatures. These coordinates are obtained from Baur's electrostatic model, and in the case of one compound (MnCl2·4H2O), from a precise three‐dimensional neutron‐diffraction study. The latter study appears to confirm the validity of Baur's model. The results indicate that the H bonds are normal bonds for all but three of the O–H‐ ‐ ‐Cl bonds which are found severely bent.

Calculations based on an electrostatic model have been made of the stabilizing energy in [F–H··F]−. The terms used have first been tested on the HF molecule and the distortion of the latter in the bifluoride ion is estimated. The calculated value of —ΔU for [F–H··F]− is 47.3 kcal. per g ion, in satisfactory accord with thermochemical estimates.

The structure of a classical one-component nonneutral plasma at low temperature confined by a magnetic field is analyzed on the basis of a simple electrostatic model assuming a shell structure. When the Madelung energy of charges is properly taken into account, the results of numerical experiments by Rahman and Schiffer are reproduced to good accuracy and the change of the structure with the confining field is predicted.

Critically evaluated experimental and theoretical atomic electron affinities are assembled and used to derive thermodynamic properties of gas-phase monatomic anions throughout the Periodic Table. The stabilities (as ΔGof) of these anions in water and liquid ammonia are calculated by a semiempirical electrostatic model. The predictions are compared with experimental observations where possible.

The physical basis for electrostatic models of relaxation at metal surfaces, including the meaning of the two parameters of the modified point-ion or α model, is discussed. The empirical α parameter is shown to produce agreement with experiment and to arise from the non-uniformity of the fixed background of electronic charge around the ions. An explicit non-uniform model of the background charge is defined which is shown to be equivalent to the successful α model and provides an example of a pure electrostatic model without empirical parameters.

The technique of pulsed-nozzle, Fourier-transform microwave spectroscopy for observing the rotational spectra of hydrogen-bonded (and other weakly bound) dimers is discussed. The sensitivity of the technique for weakly bound species and its accompanying high resolution are illustrated by reference to examples. The molecular properties of dimers that can be determined from rotational spectra via the spectroscopic constants are outlined and, in particular, the determination of geometry from rotational constants is discussed by reference to SO2⋯HF. The observed geometry for SO2⋯HF is then considered in the light of some simple rules for predicting the angular geometries of hydrogen-bonded dimers. Finally, some recent results for (SO2,HCN) are presented and the observed angular geometry is compared with the predictions of the Buckingham-Fowler electrostatic model for weakly bound dimers.

The electronic structure of 6p Hg-Ar complexes has been Investigated and described by a simple electrostatic model using the 6p average orientation with respect to the internuclear axis. The vibrational structure of the triatomic complex Hg-N2 was also described in terms of two vibrational modes, a stretching and a bending vibration. This description is essential as it is observed that the torsional modes with vibrational angular momentum Induce strong fine structure relaxation 3P1 – 3P0.

Haemoglobin is the prototype of an allosteric protein in which cooperative behaviour depends on interaction between unlike subunits. Here we present haematological and biochemical evidence that electrostatic interactions are an important determinant of haemoglobin assembly. Individuals heterozygous for positively charged beta-globin variants have a significantly lower proportion of abnormal haemoglobin than those with negatively charged variants. Moreover, these differences become more pronounced when alpha-thalassaemia is also present. Kinetic experiments using isolated chains indicate that the rate of assembly of the heterotetramer is influenced by alterations in surface charge. A simple electrostatic model is proposed in an attempt to explain these haematological and experimental findings.

The temperature coefficients of the chemical shift of /sup 51/V in carbonyl complexes in solution are reported here. For transition metal nuclei the effects of rovibrational averaging can be obtained from these temperature coefficients without gas-phase studies in the zero-pressure limit. They present a theory for the large temperature coefficients and large isotope shifts observed in transition metal complexes. They use the vibrational analysis of V(CO)/sub 6//sup -/ and Co(CN)/sub 6//sup 3 -/ to provide dynamic averages of the displacements in the V-C, C-O, Co-C, and C-N bonds as typical examples. The temperature and mass dependencies of these dynamic averages successfully account for the signs and magnitudes of the observed temperature coefficients and isotope shifts. They report observations of a correlation between the temperature coefficients and chemical shifts. This correlation is qualitatively consistent with a simple electrostatic model for shielding. The limitations of the electrostatic model for shielding are discussed.

A new switching criterion for Metal-Insulator-Si(n)-Si(p+) structures based on the MIS diode capacity is given within the framework of a simple electrostatic model. The values of the switching voltage and its dependence on temperature, together with the switching current are calculated on the basis of analytical expressions. These values are in accordance with experimental data.

Spectrophotometric and e.s.r. analyses have been carried out on the mixed-chelate complex formation equilibrium [Cu(acac)2]+[Cu(S2CNEt2)2]⇌ 2[Cu(acac)(S2CNEt2)], where acac = acetylacetonate. The equilibrium constant in non-aqueous solution is found to decrease with increasing dielectric constant of the solvent. The results are analyzed in terms of an electrostatic model in which each complex molecule is assumed to be in a cavity surrounded by uniform solvent.

X-ray photoelectron spectra have been measured for several transition-metal di- and perthiocarboxylates, and the binding energies of sulfur 2p orbitals are reported and discussed with regard to the nature of the coordination environment. “Bridging” sulfur atoms in perthiocarboxylate ligands are distinctly more positive than terminal sulfurs, and the charge distribution is consistent with a simple electrostatic model.

The enthalpy of formation of EuF 2+ in solution has been redetermined by titration calorimetry. Experiments at a constant ionic strength of μ = 1.0 M (NaClO 4 ), but at a variety of fluoride titrant concentrations, gave ΔH 101 =(9.61 ± 0.03) kJ/mol at 25 °C. This value is considerably lower than that previously reported in the literature. The corresponding entropy, however, is now consistent with an electrostatic model which has bcen shown to describe the behavior of a wide variety of metal-fluoride complexes.

For ionic amphiphiles the electrostatic interactions play an important role for the energetics of the system. At the surface of an amphiphile aggregate there is a high charge density and counterions are attracted to the surface, which has the result that the electrostatic repulsions there are reduced.

The paper is introduced by an analysis of the interrelation between the nuclear magnetic relaxation rates of the cations and anions in the same solution when the nuclear quadrupole interaction is the relaxation mechanism. The treatment is based on an electrostatic model. Higher ion-ion and ion-water correlations may cause mutual quenching or reinforcement of the relaxation effect at higher ion concentrations. Experimental results for the relaxation rates of Rb85, Rb87, Cs133, Li7, and Na23 in the ionic state are reported Most of the solutions are alkali halide solutions, partly the results regard mixed electrolyte solutions. An interpretation of the results in terms of higher ion-ion and ion-water correlations is discussed. A brief consideration of possible “electronic” contributions to the relaxation is also given. Die Arbeit wird eingeleitet durch eine Darlegung der Verknupfung zwischen den kernmagnetischen Relaxationsraten der Kationen und Anionen in derselben Losung, wenn die Kernquadrupol-Wechselwirkung den Reiaxationsmechanismus darstellt. Dieser Untersuchung liegt ein elektrostatisches Modell zugrunde. Hohere Ion-Ion- und Ion-Wasser-Korrelationen konnen bei groserer lonenkonzentration gegen-seitige Ausloschung oder Verstarkung des Relaxationseffektes verursachen. Es werden experimentelle Resultate fur die Relaxationsraten von Rb85, Rb87, Cs133, Li7 und Na23 im ionischen Zustand mitgeteilt. Die meisten der Losungen sind solche von Alkali-Halogeniden, teilweise betreffen die Resultate auch gemischte Elektrolytlosungen. Die Interpretation der Resultate auf Grund von hoheren Ion-Ion-Korrelationen wird diskutiert. Schlieslich wird eine kurze Erorterung uber mogliche “elektronische” Beitrage zum Relaxationsprozes gegeben.

Le présent article traite de quelques notions simples sur l'ouverture et la fermeture d'un contact entre un isolant et une pièce métallique portée à une haute tension, et précise l'importance des charges libres à l'interface. Un modèle électrostatique élémentaire d'un plan de charges mobiles, étendu dans deux annexes à une charge répartie dans l'épaisseur, permet de calculer l'évolution du potentiel de surface après l'ouverture du contact (déclin naturel) et après un court-circuit temporaire (retour du potentiel). L'interprétation des résultats à l'aide de ce modèle permet de caractériser l'injection de charges à l'interface, et d'estimer de façon simple la quantité et la position du centroïde des charges injectées, ainsi que la mobilité effective de ces charges.

Most of the conducting organometallic solids crystallize in the form of segregated donor and acceptor stacks. The observed metallic conductivities are the result of a partial charge transfer (i.e. incompletely filled bands). For a (semiconducting) exception and the relevant theoretical interpretation see [III.110, III. 111]. Next we present a simple electrostatic model that allows for an approximate computational treatment of segregated donor-acceptor (DA) solids (generally of quasi 1D materials) [III.34, III.112, III.113]. In DA systems with roughly comparable intra- and interchain interactions (i.e. coherent 3D solids) the k-vector must be described by three cartesian components (kx,ky,kz). The k-dependent interchain coupling opens a covalency gap ΔEC. The magnitude of ΔEC is determined by the strength of this interaction. If H⊥ is a general hopping element for the interchain interaction we have ΔEC = 2H⊥.

The compounds NH4MF3 (M= Mg, Zn, Co, Mn, Cd) have the cubic perovskite structure at high temperature, distorting to quasi-tetragonal symmetry at lower temperatures (fig. 1). In a previous communication /1/, some discrepancies between the electrostatic model and experimental data were discussed, mainly the high barrier (2000 K) to rotation of NH4 groups in NH4CdF3.

There are at least two reasons for making mathematical models of real biological systems. The first is to accurately reproduce the output of the given system in order to include it as part of a model of a larger system. The second is to construct models with real physical components capable of independent experimental verification in the hope of gaining a better understanding of the physical processes that underlie the operation of the system. The famous Hodgkin and Huxley m3 model (Hodgkin and Huxley 1952) of ion channel gating in excitable tissue is an example of the first kind. They wished to simulate the time variation of the action potential and needed a model for the time dependence of the sodium and potassium channel currents. Although later researchers attempted to put flesh on the mathematical model by trying to find the m and n particles as real physical entities, the original authors were careful to state that agreement between the predictions of the model and experiment was no guarantee that the particular model proposed was correct. It is well known that many different models may produce the same output just as a tape recorder and a flute can produce the same audible output while having nothing in common in their methods of sound production.

The structure of binary fluorides and oxides with alkali and alkaline-earth metals can be largely understood by means of the supposition of electrostatic binding forces. Thus the sequence of structure types with changing co-ordination numbers for cations and anions depending on their radial quotients, can be nearly quantitatively predicted by a simple model using electrostatically attracting and repelling forces. Moreover, the lattice energies calculated by means of the electrostatic model agree satisfactorily with those which can be experimentally determined by means of the Born-Haber cycle. The dominant role of the electrostatic binding forces decreases considerably if one changes over to the fluorides and oxides of the remaining main group and transition metals, especially when the electropositive atoms are in higher oxidation states.

The two-iron–sulphur co-ordination centre in plant and algal ferredoxins is considered as a collection of charged ions whose net negative charge is twice that of the one-iron–sulphur protein rubredoxin. Calculation of the electrostatic free-energy changes for reduction of the two types of proteins indicates that the redox potential of the two-iron–sulphur proteins should be more negative than that of the one-iron–sulphur protein and that in biological systems the ferredoxins should function as one-electron transfer proteins.

Traditionally, atomic force microscopy (AFM) experiments are conducted at tip–sample distances where the tip strongly interacts with the surface. This increases the signal-to-noise ratio, but poses the problem of relaxations in both tip and sample that hamper the theoretical description of experimental data. Here, we employ AFM at relatively large tip–sample distances where forces are only on the piconewton and subpiconewton scale to prevent tip and sample distortions. Acquiring data relatively far from the surface requires low noise measurements. We probed the CaF2(111) surface with an atomically-characterized metal tip and show that the experimental data can be reproduced with an electrostatic model. By experimentally characterizing the second layer of tip atoms, we were able to reproduce the data with 99.5% accuracy. Our work links the capabilities of non-invasive imaging at large tip–sample distances and controlling the tip apex at the atomic scale.

Second Pauling's rule, known as the electrostatic rule, has been reformulated with regard to partial net charges in covalent–ionic crystals. For more uniform treatment, an idea of atomic ionicity coefficients (AIC) related to the respective bond ionicities (BI) is introduced. The proposed definitions are consistent with crystal-chemistry principles. Examples are presented, showing how the reformulated Pauling's rule works for chosen compounds. Some other possibilities of applications of the model are also discussed. In particular, for the chosen crystals, the net charges of the ions have been calculated from a knowledge of the ionicities of the respective bonds and the BIs have been estimated from the ionic charges. A case concerning structures with non-equivalent anions is also discussed.

The electrostatic properties of zwitterionic micelles of 3-(N-hexadecyl-N,N-dimethylammonio)propanesulfonate (HPS) have been investigated by light scattering and conductivity, and a simple electrostatic model in the Debye-Hueckel approximation, containing no adjustable parameters, is presented which accounts qualitatively for the main experimental results on second virial coefficients and conductivity, as well as for fluorescence quenching reported in earlier work. Additional photochemical data concerning reprotonation rates of 8-hydroxy-1,3,6-pyrenetrisulfonate in HPS micelles are also presented and interpreted by the electrostatic model

A model based on the nuclear track potential is described and used to predict trajectories and the energy distribution of secondary ions emitted by insulating targets. In this model, the electric field generated by each track pushes away the secondary ions formed on the target surface. The effects on the potential due to target thickness, track charge density, projectile incidence angle and secondary ion mass are analyzed. Predictions are compared with experimental data existing in the literature. It is found that the proposed model describes partially the behavior observed in the angular distribution of the emitted ions and new processes are proposed to be included in the model.

The concept of hydration forces (bound water) has long been applied to colloid science and its biological applications1–11. While these repulsive forces have been demonstrated experimentally in many cases1,2,6–11 our understanding of them remains uncertain3–5,12. Their best definition is perhaps as the discrepancy between experimental results and the currently accepted Gouy–Chapman–Stern/Derjaguin–Landau–Verwey–Overbeek (GCS/ DLVO) theories. We have found that a new repulsive force is predicted by application of the Debye–Huckel–Manning (DHM) approach to double-layer overlap13–15 using the ion-binding/ion-bouncing model (IBBM)15. This new force arises when overlapping double layers approach each other in such a way that the co–ions are completely expelled and counter-ions are squeezed into a smaller volume. The magnitude of these repulsions is of the order of hundreds of atmospheres at close separations. We therefore question the current interpretations of these forces with the warning that the electrostatic model outlined below needs further elaboration for neutral and weakly charged surfaces16,17.