Ab Initio Calculations and Molecular Dynamics Simulations for Imidazolium – [Tf2N] Ionic Liquids: Microscopic Structure and Thermodynamic Properties

Ionic liquids (IL) have received considerable attention by the chemical industry in recent years, mostly towards the development of environmentally benign processes. Selection of an IL for a specific process and subsequent detailed process design and process simulation require accurate knowledge of the physical properties of the IL. Atomistic simulation using realistic force fields provides a reliable tool for the calculation of such properties.

In this work, microscopic structure, dynamic and thermodynamic properties of imidazolium-based ILs are calculated. Ab initio density functional theory (DFT) calculations are performed for [bmim][Tf2N], [hmim][Tf2N] and [omim][Tf2N] in order to evaluate the minimum energy structure and calculate the charge density distribution of the molecules. The electrostatic potential obtained is incorporated into the CHARMM atomistic force field that is used subsequently for Molecular Dynamics (MD) simulations. Mass densities obtained for the three ILs over a wide temperature and pressure range are in excellent agreement with experimental data. In addition, the microscopic static and dynamic structure of the ILs is examined. Finally, the solubility of carbon dioxide in the ILs is calculated using the Widom insertion methodology. Predictions are in excellent agreement with experimental data.