Local composition in binary mixtures of Lennard-Jones fluids with differing sizes of components

Three Lennard-Jones binary liquid mixture systems obeying Lorentz-Berthelot rules, but having differing component sizes and energy parameters, have been used to calculate the local fractions of the two components around each type of central particle over the entire composition range from molecular-dynamics data. It is found that well-defined local fractions can be determined even in the case where the size difference between the particles is large. The results obtained are compared with values predicted by the Wilson and NRTL equations. It is confirmed that the NRTL equation gives satisfactory agreement only in the case of mixtures of components having the same size parameters. A new correlation is proposed by a modification of the NRTL equation. This correlation can predict reasonably well local-fraction data for all the Lennard-Jones liquid mixtures studied so far.     

Alternating-current ionic conduction and dielectric relaxation of poly(vinylidene fluoride) at high temperatures

Dielectric properties of poly(vinylidene fluoride) have been studied in the frequency range 20 Hz to 1 MHz and between 100 and 220°C, during heating and cooling. The dielectric constant and loss change abruptly at the temperature T_m corresponding to the melting point. At lower frequencies, two types of ionic conductin are observed. One appears below T_m and is attributed to interfacial polarization. The other occurs above T_m and is related to electrode polarization. These results suggest that a crystalline polymer is a heterogeneous medium for ionic transport, while the melt is a homogeneous medium. From these results, the nature of ac ionic conduction in crystalline polymers is discussed. At high frequency, the α relaxation is observed below T_m. It is due to the molecular motion in the crystalline region and disappears at T_m.     

Alternating copolymerization of polar vinyl monomers in the presence of zinc chloride. II. Properties of acrylonitrile–styrene copolymer

The properties of the acrylonitrile–styrene copolymer prepared in the presence of zinc chloride were investigated in comparison with those of a copolymer having the same overall composition and prepared by the ordinary radical procedure. The characteristics of the polymer prepared with ZnCl₂ were as follows: (1) less coloration by alkali treatment, (2) less coloration by thermal treatment and (3) higher glass transition temperature. These features may be attributed principally to the structure of the copolymer, which has more unlike bonds and less long sequences as described in the first article of this series. The effects of residual salt in the copolymer on the properties were also investigated.     

Initial quantum levels of captured muons in CO,CO2, and COS

The role of valence electrons for the muon capture process by molecules is experimentally investigated with the aid of cascade calculations. Low-momentum muons are introduced to gas targets of CO, CO₂, and COS below atmospheric pressure. The initial states of captured muons are determined from the measured muonic X-ray structure of the Lyman and Balmer series. We propose that the lone pair electrons in the carbon atom of CO significantly contribute to the capture of a muon with large angular momenta.

     

Hydration structure around a non-electrolyte molecule as revealed by monte carlo calculation: have you seen the “iceberg”?

Monte Carlo calculations have been carried out for pure water and an infinitely dilute aqueous solution of methanol at 298.15 K at ordinary density by the Metropolis method in NTV ensemble. The hydration structure around methanol revealed by a graphic display technique indicates a structure-forming effect near the hydrophobic group.     

Four-m calculations on methanol-water solutions

The structural characteristics of methanol in aqueous solutions, on a molecular level, can be elucidated by four types of calculation: molecular orbital, multiparametric optimization of intermolecular potential function, Monte Carlo, and molecular dynamics. As a first step, the potential between water and methanol was determined by ab initio LCAO SCF molecular orbital calculations with the STO—3G basis set and subsequent multiparametric fitting. This and water—water potentials were used for Monte Carlo calculation on an aqueous methanol solution containing a 1:216 mole ratio of methanol to water. Hydration around methanol is briefly discussed.