Equilibrium gas-phase structures of sodium fluoride, bromide, and iodide monomers and dimers

The alkali halides sodium fluoride, sodium bromide, and sodium iodide exist in the gas phase as both monomer and dimer species. A reanalysis of gas electron diffraction (GED) data collected earlier has been undertaken for each of these molecules using the EXPRESS method to yield experimental equilibrium structures. EXPRESS allows amplitudes of vibration to be estimated and correction terms to be applied to each pair of atoms in the refinement model. These quantities are calculated from the ab initio potential-energy surfaces corresponding to the vibrational modes of the monomer and dimer. Because they include many of the effects associated with large-amplitude modes of vibration and anharmonicity, we have been able to determine highly accurate experimental structures. These results are found to be in good agreement with those from high-level core-valence ab initio calculations and are substantially more precise than those obtained in previous structural studies

Effective electromagnetic properties of microheterogeneous materials with surface phenomena

In this paper, we present an approach to calculate the complex dielectric permittivity of a micro-heterogeneous medium composed of non-conductive solid inclusions embedded into the conductive liquid continuous host. To take into account the surface effects, we approximate the inclusion by a layered ellipsoid consisting of a dielectric core and an infinitesimally thin outer shell corresponding to an electrical double layer (EDL). To predict the effective complex dielectric permittivity of materials with a high concentration of inclusions, we have modified the Effective Field Method (EFM) for the layered ellipsoidal particles with complex electrical properties. We present the results of complex permittivity calculations for the composites with randomly and parallel oriented ellipsoidal inclusions. To analyze the influence of surface polarization, we have accomplished modeling in a wide frequency range for different existing physic-chemical models of double electrical layer. The results obtained show that the tensor of effective complex permittivity of a micro-heterogeneous medium with surface effects has complicate dependences on the component electrical properties, spatial material texture, and the inclusion shape (ellipsoid aspect ratio) and size. The dispersion of dielectric permittivity corresponds to the frequency dependence for individual inclusion of given size, and does not depend on the inclusion concentration