Interaction potentials for the alkali ion—rare-gas systems

The alkali ion—rare-gas interaction potentials are determined directly from gaseous ion transport data. The potentials are tested by calculating the transport coefficients from them and then comparing the calculated values with the many sets of measured values. Similar tests are made of other potentials that have been proposed, especially those inferred from alkali ion—beam-scattering measurements in the rare gases. These tests indicate that the present potentials are generally accurate within 10% over wide ranges of ion—rare-gas separation.     

Interaction potentials for Li+—rare-gas systems

The accuracies of proposed interaction potentials for the Li⁺—rare-gas systems are tested by comparing the transport coefficients calculated from the potentials with the experimental values. The agreement is generally good for theoretical potentials that take electron correlation into account and for potentials inferred from ion-beam measurements of high accuracy, except where the transport data are primarily influenced by the long-range tail of the potential. The transport data are also used to directly determine the Li⁺—rare-gas interaction potentials, with an estimated accuracy of 10% over wide ranges of ion—atom separation.     

On the interatomic potentials for noble gas mixtures

Recently, a relatively simple scheme for the construction of isotropic intermolecular potentials has been proposed and tested for the like species interactions involving He, Ne, Ar, Kr and H₂. The model potential has an adjustable parameter which controls the balance between its exchange and Coulomb energy components. The representation of the Coulomb energy contains a damped multipolar dispersion energy series (which is truncated through O(R^?10) and provides additional flexibility through adjustment of the dispersion energy coefficients, particularly C₈ and C₁₀, within conservative error estimates. In this paper the scheme is tested further by application to interactions involving unlike noble gas atoms where the parameters in the potential model are determined by fitting mixed second virial coefficient data as a function of temperature. Generally the approach leads to potential of accuracy comparable to the best available literature potentials which are usually determined using a large base of experimental and theoretical input data. Our results also strongly indicate the need of high quality virial data.     

Solvent-averaged potentials for alkali-, earth alkali-, and alkylammonium halide aqueous solutions

We derive effective, solvent-free ion-ion potentials for alkali-, earth alkali-, and alkylammonium halide aqueous solutions. The implicit solvent potentials are parametrized to reproduce experimental osmotic coefficients. The modeling approach minimizes the amount of input required from atomistic (force field) models, which usually predict large variations in the effective ion-ion potentials at short distances. For the smaller ion species, the reported potentials are composed of a Coulomb and a Weeks-Chandler-Andersen term. For larger ions, we find that an additional, attractive potential is required at the contact minimum, which is related to solvent degrees of freedom that are usually not accounted for in standard electrostatics models. The reported potentials provide a simple and accurate force field for use in molecular dynamics and Monte Carlo simulations of (poly-)electrolyte systems.     

Investigation of the aqueous lithium and magnesium halide systems

The solubilities of the system LiBr–MgBr₂–H₂O have been investigated at 25°C and 50°C. It is established that the system is of a simple eutonic type. Pitzer's model is used for calculating the thermodynamic functions needed for plotting the solubility isotherms of the systems LiX–MgX₂–H₂O (X=Cl, Br) at 25°C. According to calculations made, the Gibbs energy of formation of LiCl·MgCl₂·7H₂O from simple salts is _rG°_m=–2.01 kJ-mol^–1, while the value _fG°_m=–2748 kJ-mol^–1 corresponds to formation from the elements.     

Fabrication of high-precision silver halide layers for nanoscale linear-and angular-translation measurement systems

A silver halide emulsion casting technique was designed and studied for the fabrication of thin holographic layers of 3 ± 0.5 μm thickness free of phase distortions and with the required resolving power depending on the optical-range wavelength in the holographic recording of metrological gratings.     

Thermodynamic transferability of coarse-grained potentials for polymer-additive systems

In this work we study the transferability of systematically coarse-grained (CG) potentials for polymer-additive systems. The CG nonbonded potentials between the polymer (atactic polystyrene) and three different additives (ethylbenzene, methane and neopentane) are derived using the Conditional Reversible Work (CRW) method, recently proposed by us [Brini et al., Phys. Chem. Chem. Phys., 2011, 13, 10468-10474]. A CRW-based effective pair potential corresponds to the interaction free energy between the two atom groups of an atomistic parent model that represent the coarse-grained interaction sites. Since the CRW coarse-graining procedure does not involve any form of parameterisation, thermodynamic and structural properties of the condensed phase are predictions of the model. We show in this work that CRW-based CG models of polymer-additive systems are capable of predicting the correct structural correlations in the mixture. Furthermore, the excess chemical potentials of the additives obtained with the CRW-based CG models and the united-atom parent models are in satisfactory agreement and the CRW-based CG models show a good temperature transferability. The temperature transferability of the model is discussed by analysing the entropic and enthalpic contributions to the excess chemical potentials. We find that CRW-based CG models provide good predictions of the excess entropies, while discrepancies are observed in the excess enthalpies. Overall, we show that the CRW CG potentials are suitable to model structural and thermodynamic properties of polymer-penetrant systems.     

Development of interatomic ReaxFF potentials for Au-S-C-H systems

We present fully reactive interatomic potentials for systems containing gold, sulfur, carbon, and hydrogen, employing the ReaxFF formalism. The potential is designed especially for simulating gold-thiol systems and has been used for studying cluster deposition on self-assembled monolayers. Additionally, a large number of density functional theory calculations are reported, including molecules containing the aforementioned elements and adsorption energetics of molecules and atoms on gold.     

Analysis of Lippmann diagrams: Binary alkali halide systems

Summary From the analysis of solubility diagrams information on excessG functions at 298.15K of binary common ion alkali halide mixed crystals can be obtained. With additional data on enthalpies of mixing andG values derived from the liquidus curve, a correlation between excess enthalpies and entropies is established which can be employed to predict phase diagrams of other systems.

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Analyse von Lippmann-Diagrammen: Binäre Alkalihalogenidsysteme

Zusammenfassung Aus der Analyse von Löslichkeitsdiagrammen kann man Informationen über Excess-G-Funktionen binärer Alkalihalogenid-Mischkristalle bei 298.15 K erhalten. Zusammen mit experimentellen Mischungsenthalpien undG-Werten, die aus den Liquiduskurven abgeleitet wurden, läßt sich eine Korrelation zwischen Excessenthalpien und -entropien aufstellen, die zur Vorhersage von Phasendiagrammen anderer Systeme verwendet werden kann.

     

Frequency dependence of potentials of minimum capacitance for electrodes of copper subgroup metals in alkali halide melts

The electrochemical impedance technique was use to obtain the potentials of the minimum capacitance of Cu, Ag, and Au electrodes in chlorides, bromides, and iodides of sodium, potassium, and cesium. Their dependence on the nature of the metal and electrolyte, temperature and ac signal frequency is studied. It is shown that the potential of the minimum capacitance tends at a decrease in the frequency to the zero charge potential measured under similar conditions. An assumption is ventured that the cause of this may be specific adsorption of halide ions on the electrode in the form of negatively charged dihalide complexes. It is found that in the systems where two minimums are observed, a decrease in the spacing between the cathodic and anodic minimums correlates with an increase in the strength of the metal-adsorbate bond.     

Rotational mechanism for vibrational relaxation in rigid media. Interaction potentials

Using the assumption of pairwise additive forces we derive the interaction potential acting upon a substantial impurity in a crystalline lattice. The angle dependent parts of the force on the impurity internal vibrations are represented in the form of a Fourier series. Numerical calculations of the Fourier coefficients of the force are presented for a model system employing empirical argon—argon interactions. The higher Foutier coefficients are shown to decrease rapidly in conformity with the simple model potential used to describe the vibrational relaxation in a preceding paper.     

Interaction potentials for UF6 with itself and with rare-gas atoms

Potential curves have been calculated for the UF₆-UF₆ and UF₆-rare gas atom interactions using statistical models for the UF₆ charge density and the intermolecular interaction. Agreement with available experimental data is good.     

Recent insights for achieving mixed halide perovskites without halide segregation

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Photocyclization of carvone to carvone camphor using rare gas halide lasers

The intramolecular photocyclization of (-)carvone with rare gas halide lasers is decribed. A 70-fold increase in quantum yield is observed at an intensity of 60 MW/cm², which is rationalized in terms of consecutive two-photon absorption. The mechanism proposed also describes the product distribution, which is different from that obtained by lamp irradiation.     

Esterification and etherification by silver oxide-organic halide reaction gas chromatography.

In an attempt to separate a number of methylated nucleoside constituents reportedly present in various mammalian RNA preparations, a comparison of the migration of selected nucleoside standards was assessed via thin-layer chromatographic techniques with respect to three solvent systems and an adsorbent of varying proportions of silica gel and microcrystalline cellulose. The results of these studies revealed that a mixture of seventeen methylated constituents could be separated following two-dimensional development on an adsorbent containing 60% cellulose and 40% silica gel. Constituents separated included the 2'-O-methylated derivatives of adenosine, guanosine, cytidine and uridine, 1-, N6- and N6,N6-methyladenosines, 1-methylinosine, 1-, 7-, N2- and N2,N2-methylguanosines, 3-, 4- and 5-methylcytidines and 3- and 5-methyluridines. In addition, all of the above constituents were separated from their respective non-methylated nucleosides and bases.     

Solid solutions in binary halide systems having a common anion

Deviations of experimental liquidus curves from ideal curves calculated by the Schröder equation are analyzed for halides that form eutectic systems and systems containing solid solutions. Analysis of phase diagrams shows that the key factors for solid solution formation in binary halide systems having a common anion are as follows: component crystal lattices and close values of the effective radii and polarizing powers of the cations.     

The response of halide ion-selective electrodes to redox systems : A comparison between silver/silver halide electrodes and silver sulphide- based halide ion-selective electrodes

Silver/silver chloride and bromide electrodes, prepared by anodizing ordinary silver electrodes, and the corresponding ion-selective electrodes based on silver sulphide, were tested for their susceptibility towards redox systems. It proved that the latter type of electrode responded significantly to strong oxidants. In contrast, the silver/silver halide types were highly resistant to redox interference provided that the silver halide layer was free from open pores. This could be achieved by generation of sufficiently thick layers and by selection of suitable current densities during electrodeposition (<20 mA cm^-2). The interrelation between the conditions of silver chloride film generation and redox resistance of the resulting electrodes is described in detail.