Molecular dynamics study of Na+and Cl−in methanol

Influence of electric field on the hydrogen bond network of methanol

The understanding of the structure of hydrogen (H) bonding liquids in electric (E) fields is important in the context of several areas of research, such as electrochemistry, surface science, and thermodynamics of electrolyte solutions. We had earlier presented a general thermodynamic framework for this purpose, and had shown that the application of E field enhances H-bond interactions among water molecules. The present investigation with methanol suggests a different result-the H-bond structure, as indicated by the average number of H bonds per molecule, goes through a maxima with increasing field strength. This result is explained based on the symmetry in the location of the H-bonding sites in the two types of molecules.

Structure and Dynamics of Br- Ion in Liquid Methanol

A Car-Parrinello molecular dynamics simulation has been performed on a solution of Br- in liquid methanol analyzing with particular attention charge transfer and polarization effects. The first solvation shell has been characterized in terms of H-bonds, and it has been found that the high polarization of the bromide gives rise to a stable solvent cage. The differences in the coordination number with the chloride can be ascribed to the ionic radius and to the stronger perturbations brought by the solvent to the bromide ion.

Solvation Dynamics of Li+ and Cl- Ions in Liquid Methanol

Car-Parrinello molecular dynamics simulations have been performed on Li(+) and Cl(-) in fully deuterated liquid methanol. The results have been compared with available experimental and theoretical data. It has been found that the lithium cation has a stable tetrahedral coordination, whereas the chloride anion presents an average coordination number of 3.56. The polarization effects induced by the ion on the solvent have been analyzed in terms of Wannier function centers. Particular attention has been devoted to the charge transfer, which is particularly important in these types of systems. Evidence for the stability of the lithium cation solvent cage also has been found in the vibrational spectra.

Electric conductivities of 1:1 electrolytes in liquid methanol along the liquid-vapor coexistence curve up to the critical temperature. II. KBr and KI solutions

The molar conductivities Lambda of KBr and KI in dilute methanol solutions were measured along the liquid-vapor coexistence curve up to the critical temperature (240 degrees C). The concentration dependence of Lambda in each condition was analyzed by the Fuoss-Chen-Justice equation to obtain the limiting molar conductivities and the molar association constants. Using the present data together with the literature ones, the validity of the Hubbard-Onsager (HO) dielectric friction theory based on the sphere-in-continuum model was examined for the translational friction coefficients zeta of the halide ions (the Cl(-), Br(-), and I(-) ions) in methanol in the density range of 2.989rho(c)> or =rho> or =1.506rho(c), where rho(c)=0.2756 g cm(-3) is the critical density of methanol. For all the halide ions studied, the friction coefficient decreased with decreasing density at rho>2.0rho(c), while the nonviscous contribution Deltazeta/zeta increased; Deltazeta was defined as the difference between zeta and the friction coefficient estimated by the Stokes law. The density dependence of zeta and Deltazeta/zeta were well reproduced by the HO theory at rho>2.0rho(c). The HO theory also explained the ion-size dependence of Deltazeta/zeta which decreased with ion-size at rho>2.0rho(c). At rho<2.0rho(c), on the other hand, the HO theory could not explain the density and the ion-size dependences of zeta and Deltazeta/zeta. These results indicated that the application limit of the HO theory lied about rho=2.0rho(c) which is the same as the application limit observed for the alkali metal ions. The present results were also compared with the results in subcritical aqueous solutions.