| Popis: |
In the last several years, RTILs have become an interesting class of solvents for different chemical applications and required a better understanding of their physical and chemical properties. The family of ILs based on imidazolium cations has been intensively investigated due to their desirable physical and chemical properties. A number of experimental and theoretical studies of imidazolium-based ILs have focused on understanding the interactions between different types of ILs and water solvent. Understanding such interaction is of great importance because ILs can absorb a large amount of water from the atmosphere. This is relevant due to the fact that even low levels of water in ILs can dramatically change their physical and chemical properties such as viscosity, density conductivity and solvating ability. The aim of this work is to study the structural and dynamical properties of the ionic liquid 1-decyl-3-methyl-imidazolium chloride ([DMim][Cl]) and investigate how they are affected by the presence of water molecules. The main results: A first interesting results is that, as judged from the density of the system, quite long MD simulation time are required at 350 K to reach equilibrium for the pure ionic liquid system; Analysis of the radial and spatial distribution functions for the pure ionic liquid system reveals that the addition of water to [DMim][Cl] leads to a variation in the structural organization. In details, the spatial distribution functions reveal that at higher water content there is a higher degree of order among the organic cations. This indicates that addition of water induces structuring of the system. The results of the present work indicates that the value of the diffusion constant varies up to 2 orders of magnitude depending on the time interval used for its calculation. Interestingly, when the diffusion constant is calculated using a short time interval the results obtained are in line with those reported previously in the literature dealing with the simulation of similar systems; If the calculation of the diffusion constant is performed over large time interval (several hundreds of ns), much smaller diffusion constant are obtained, and the agreement with the experimental data is unfortunately worsened. |
