Molecular dynamics simulations of aqueous LiCl solution have been carried out over wide concentration (from 0.1 to 11.4 mol/kg) and temperature (from -30 to 110 °C) ranges. Three different interaction potentials are investigated: the recent Li + -water effective pair potential, derived from ab initio molecular dynamics simulations [

To study the effects of water on conformational dynamics of polyalcohols, Molecular Dynamics simulations of glycerol-water liquid mixtures have been carried out at different concentrations: 42.9 and 60.0 wt % of glycerol, respectively. On the basis of the analysis of backbone conformer distributions, it is found that the surrounding water molecules have a large impact on the populations of the glycerol conformers. While the local structure of water in the liquid mixture is surprisingly close to that in pure liquid water, the behavior of glycerols can be divided into three different categories where roughly 25% of them occur in a structure similar to that in pure liquid of glycerol, ca. 25% of them exist as monomers, solvated by water, and the remaining 50% of glycerols in the mixture form H-bonded strings as remains of the glycerol H-bond network. The typical glycerol H-bond network still exists even at the lower concentration of 40 wt % of glycerol. The microheterogeneity of water-glycerol mixtures is analyzed using time-averaged distributions of the sizes of the water aggregates. At 40 wt % of glycerol, the cluster sizes from 3 to 10 water molecules are observed. The increase of glycerol content causes a depletion of clusters leading to smaller 3-5 molecule clusters domination. Translational diffusion coefficients have been calculated to study the dynamical behavior of both glycerol and water molecules. Rotational-reorientational motion is studied both in overall and in selected substructures on the basis of time correlation functions. Characteristic time scales for different motional modes are deduced on the basis of the calculated correlation times. The general conclusion is that the presence of water increases the overall mobility of glycerol, while glycerol slows the mobility of water.

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As the development of the work (J. Phys. Chem. B 2019, 123 (10), 2362−2372), we have investigated the translational mobility in the same set of dried imidazoliumbased ionic liquids (ILs) [bmim]A (A = BF 4− , NO 3 − , TfO − , I − , Br − , and Cl − ) in a wide temperature range using the NMR technique. It is shown that for the [bmim] + cation, the temperature dependencies of product Dη do not follow the Stokes−Einstein relation for most systems studied, that is, the so-called "diffusion−viscosity decoupling" was realized. The correlation between local and translational mobility in pure IL of the [bmim][A] type was investigated using the data on NMR relaxation rates and diffusion coefficients. The most recent hypothesis of "water pockets" in mixtures of IL with water is critically discussed. Considering the totality of data in the literature and obtained here, we propose a specific model of the microstructure which may be applied up to water concentrations of 80−90 mol % (the structure of water-rich solutions is out of our current consideration). To confirm the model, molecular dynamics simulations of "IL−water" mixtures were also carried out.

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Small water clusters, containing ions, have been studied using molecular dynamics simulations at temperatures ranging from 0 to 250 K. The simulations are carried out systematically by varying the ion size, shape, and charge as well as the cluster size and the initial configuration. Transitions between solid and liquid phases are followed to study the effects of the ions on the cluster melting temperature, compared to pure water clusters of the same size. The effect of the ion on the ice-cluster melting appears to be a complicated process which depends simultaneously on a variety of factors, such as the initial cluster configuration and the ion position inside the cluster as well as the ion mass, size and its charge. In the case of monovalent cations the most important characteristics for the cluster evolution is the ion mass, while for divalent cations the ion charge is the most dominant factor. In the case of negatively charged ions the main factor of the system evolution is the ion size. Two principally different types of cluster structures can be observed from the simulations: The peripheral structure where the ion takes up a position, preferably on the cluster surface and the interior structure where the ion prefers the center of the system. The peripheral structure is typical for clusters containing the small monovalent Li+ cation but also for those containing the large Cl− anion, while divalent cations, large monovalent Na+ cation and small F− anions gave rise to the interior type of structure. Generally, an increase of the ion size changes the cluster structure making the peripheral variant more preferable.

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