Relation Between the Diffusivity, Viscosity, and Ionic Radius of LiCl in Water, Methanol, and Ethylene Glycol: A Molecular Dynamics Simulation

Abstract

A molecular dynamics (MD) investigation of LiCl in water, methanol, and ethylene glycol (EG) at 298 K is reported. Several structural and dynamical properties of the ions as well as the solvent such as self-diffusivity, radial distribution functions, void and neck distributions, velocity autocorrelation functions, and mean residence times of solvent in the first solvation shell have been computed. The results show that the reciprocal relationship between the self-diffusivity of the ions and the viscosity is valid in almost all solvents with the exception of water. From an analysis of radial distribution functions and coordination numbers the nature of hydrogen bonding within the solvent and its influence on the void and neck distribution becomes evident. It is seen that the solvent−solvent interaction is important in EG while solute−solvent interactions dominate in water and methanol. From Voronoi tessellation, it is seen that the voids and necks within methanol are larger as compared to those within water or EG. On the basis of the void and neck distributions obtained from MD simulations and literature experimental data of limiting ion conductivity for various ions of different sizes, we show that there is a relation between the void and neck radius on the one hand and dependence of conductivity on the ionic radius on the other. It is shown that the presence of large diameter voids and necks in methanol is responsible for maximum in limiting ion conductivity (λ0) of TMA+, while in water and EG, the maximum is seen for Rb+. In the case of monovalent anions, maximum in λ0 as a function ionic radius is seen for Br− in water and EG but for the larger ClO4 − ion in methanol. The relation between the void and neck distribution and the variation in λ0 with ionic radius arises via the Levitation effect which is discussed. These studies show the importance of the solvent structure and the associated void structure.

A comparison of classical interatomic potentials applied to highly concentrated aqueous lithium chloride solutions

“…[24] (with 5 different water models, none of them is TIP4P), or in Ref. [26] (with ethylene glycol).…”

“…There are several comprehensive studies (such as [4,22,23]) concerning the adaptability of these models, yet the ionic parameter sets are often chosen almost randomly, and/or ionic force field parameters developed for other (different) water models are combined (see e.g. [24][25][26][27]).…”

Density of Methanolic Alkali Halide Salt Solutions by Experiment and Molecular Simulation

“…This orientation was also observed in simulation studies in the literature. [31][32][33]44 The comparison between the position of the first maximum r max,1 in the RDF 44,46 and from the comparison of experimental g i−O (r) data. 91 The good agreement between the experimental data and the predictions from molecular simulation of the reduced density of the alkali halide salt solutions (cf.…”

Aggregation of Molecules in Liquid Ethylene Glycol and Its Manifestation in Experimental Raman Spectra and Non-Empirical Calculations

“…1, for tetrameric and higher-order aggregates, those intramolecular hydrogen bonds become weaker). This means that the CH 2 OH groups are rotated with respect to each other, which is associated with a potential barrier arising owing to the interaction between the OH bonds at the ends of the molecule [11,12]. In addition, there is also a strong interaction of the hydrogen atoms in the CH 2 OH groups with the oxygen atoms; more specifically, of the hydrogen H 8 and H 5 atoms with the oxygen O 4 and O 2 atoms, respectively.…”