New applications of integral equations methods for solvation continuum models: ionic solutions and liquid crystals

We present a new method for solving numerically the equations associated with solvation continuum models, which also works when the solvent is an anisotropic dielectric or an ionic solution. This method is based on the integral equation formalism. Its theoretical background is set up and some numerical results for simple systems are given. This method is much more effective than three‐dimensional methods used so far, like finite elements or finite differences, in terms of both numerical accuracy and computational costs. This revised version was published online in July 2006 with corrections to the Cover Date.     

Surface-functionalized ionic liquid crystal-supported ionic liquid phase materials: ionic liquid crystals in mesopores

The influence of confinement on the ionic liquid crystal (ILC) [C(18)C(1)Im][OTf] is studied using differential scanning calorimetry (DSC), polarized optical microscopy (POM), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The ILC studied is supported on Si-based powders and glasses with pore sizes ranging from 11 to 50 nm. The temperature of the solid-to-liquid-crystalline phase transition seems mostly unaffected by the confinement, whereas the temperature of the liquid-crystalline-to-liquid phase transition is depressed for smaller pore sizes. A contact layer with a thickness in the order of 2 nm is identified. The contact layer exhibits a phase transition at a temperature 30 K lower than the solid-to-liquid-crystalline phase transition observed for the neat ILC. For applications within the "supported ionic liquid phase (SILP)" concept, the experiments show that in pores of diameter 50 nm a pore filling of α>0.4 is sufficient to reproduce the phase transitions of the neat ILC.     

On polarization in ionic crystals

Permittivities (ɛ) of LiF, NaCl, and KBr ionic crystals of various dispersities were measured. A progressive increase of ɛ up to ∼10⁵ with the dispersity of crystals was detected. A conclusion was drawn that this effect needs to be considered when determining effective charges on atoms by Szigeti’s method in the case of measuring ɛ of the powders.     

Covalent bonds in ionic crystals

An ion at a tetrahedral site will develop an induced octupole moment, which is equivalent to a covalent bond. The magnitude of this bond is calculated For AgI and the copper halides, and removes a discrepancy between theory and experiment which has stood for 47 years.     

1,10-Phenanthrolinium ionic liquid crystals

The 1,10-phenanthrolinium cation is introduced as a new building block for the design of ionic liquid crystals. 1,10-Phenanthroline, 5-methyl-1,10-phenanthroline, 5-chloro-1,10-phenanthroline, and 4,7-diphenyl-1,10-phenanthroline were quaternized by reaction with 1,3-dibromopropane or 1,2-dibromoethane. The resulting cations were combined with dodecyl sulfate or dioctyl sulfosuccinate anions. The influence of both the cation and anion type on the thermal behavior was investigated. Several of the complexes exhibit mesomorphic behavior, with smectic E phases for the dodecyl sulfate salts and smectic A phases for the dioctyl sulfosuccinate salts. Structural models for the packing of the 1,10-phenanthrolinium and anionic moieties in the liquid-crystalline phases are presented. The ionic compounds show fluorescence in the solid state and in solution.     

Interfacial free energies of ionic crystals

Minimum values of the liquid-crystal interfacial free energy have been obtained from data on the maximum supercooling of small droplets of solutions of ionic crystals.     

Preliminary communication Hydrogen-bonded ionic liquid crystals

Ionic and non-ionic building units were connected via hydrogen bonds. Stable liquid crystalline phases were obtained by a suitable choice of the units. The ionic associates are not miscible with the respective non-ionic associates.     

Binding in purely ionic univalent crystals

A simple expression for the crystal lattice energy of A(I)B(VII) crystals is proposed using an indeterminacy principle. The suggested approach gives acceptable results.     

Radiation resistance of ionic and ionic-molecular crystals

The factors that determine the stability of ionic and ionic-molecular crystals in ionizing radiation fields are analyzed. The concepts of the fundamental reactivity (stability) of a solid (the ability of the ideal crystal lattice of the material, in which only intrinsic point defects—interstitial ions and vacancies—are present, to undergo radiation-chemical degradation) and the structure-sensitive reactivity determined by the presence of structural and extrinsic defects are introduced. Data on the radiation resistance of crystalline solids (alkali halides, silver halides, and silver azide) are summarized. It is pointed out that the AgHal crystalline matrix should be resistant toward radiation and alkali halide and AgN₃ crystals should not.     

X-Ray scattering study of ionic colloidal crystals

The scattering study of ionic colloidal crystals by using one- and two-dimensional ultra-small-angle scattering techniques is reviewed with a special reference to dilute dispersions. Because of large lattice constants of colloidal crystals, ultra-small angle regions need to be covered either by long distance optical systems combined with a synchrotron X-ray source or by adopting the Bonse–Hart optics. The crystal structure, lattice constant, and crystal orientation can be precisely determined.     

Metal-containing ionic liquids and ionic liquid crystals based on imidazolium moiety

Ionic liquids and ionic liquid crystals of imidazolium salts composed of various transition and main group metals have been reviewed. Ionic metal complexes of imidazoles and N-heterocyclic carbenes possess the similar properties were also included. These types of ILs and ILCs have been realized as potential solvents, catalysts, catalyst precursors and reagents for many organic transformations and provide ecofriendly protocols. They have also been found to play key roles in material science. Many of these IL systems are air- and moisture stable and are considered as alternatives for air- and moisture sensitive chloroaluminate-based ILs.     

Lattice energy estimation for inorganic ionic crystals

An empirical method based on chemical bond theory for the estimation of the lattice energy for ionic crystals has been proposed. The lattice energy contributions have been partitioned into bond dependent terms. For an individual bond, the lattice energy contribution made by it has been separated into ionic and covalent parts. Our calculated values of lattice energies agree well with available experimental and theoretical values for diverse ionic crystals. This method, which requires detailed crystallographic information and elaborate computation, might be extended and possibly yield further insights with respect to bond properties of materials.     

Mechanism of metallization of ionic crystals by pressure

Experimental data on the compressibility of the high-pressure phases of a number of ionic crystals were used to calculate the energies of compression corresponding to the energies of atomization of these substances. It was found that interatomic distances in the compressed substances are equal to the sum of radius of the metal cation and the covalent radius of the nonmetal atom. The mechanism of the metallization of ionic crystals, in particular, the sources of delocalized electrons, was discussed.     

Defect-assisted conductivity in organic ionic plastic crystals

In order to determine the role of defects (vacancies and extended lattice defects) in the conductivity mechanism of a well studied organic ionic plastic crystal electrolyte, conductivity and mean defect volumes were measured. The ionic conductivity of the salt showed a characteristic phase dependence. Defect volumes, as measured by positron annihilation lifetime spectroscopy, showed increasing rates of expansion with increasing rotational disorder. The dependence of ionic conductivity on defect volume was observed to be phase dependent. Increases in mean defect volume size below approximately 100 cm(3) mol(-1) did not always facilitate ionic conductivity. It was shown that the material undergoes a solid-solid phase transition to the most disordered phase (a plastic crystalline phase with the highest conductivity) when the mean defect volume becomes larger than the molar volume of either the rotating anionic or cationic species. Conductivity in this phase had the strongest dependence on defect volume. Critical volumes calculated from the free volume model of Cohen and Turnbull were unrealistically large.     

Cluster approximation for covalent and ionic-covalent crystals

Suggested earlier technique of taking into account the boundary conditions for crystal structures with a significant constituent of a chemical bond has been realized basing on the method of high order finite differences. The consideration is carried out on the example of impurity substitution centers in GaAs (Si) and Si (P, S) crystals. Rather good agreement with the experimental results and the crystal approach has been achieved.     

Lorentz factors and surface permittivity of ionic crystals

The explicit analytical expressions and the corresponding numerical scheme are proposed for the calculation of Lorentz factors (LF) in ideal ionic crystals. Formulae for the permittivity tensors and local fields based on the calculated LF are given for a number of crystal types, including such as CsCl, NaCl, CaF₂ and ZnS, where Clausius–Mossotti and the addition rules are valid, and others, like Cu₂O, TiO₂, perovskite, wurtzite where the violation of both rules is common. The equations for the wave-vector-dependent permittivity in infinite crystals and for surface and lone layer permittivity are derived, and sample numerical calculations of the bulk, surface, and single layer permittivity are in a reasonable agreement with the data of measurements if the crystal structure parameters and ions' polarizabilities are used as the input data.