In this thesis, molecular dynamics simulation and quantum chemistry calculations have been used to study of the thermodynamics, structural, dynamical, and traort properties of four ionic liquids based on the imidazolium cation and bis(trifluoromethanesulfonyl)imide anion. Molecular dynamics is a method for the simulation of thermodynamic behavior of materials in three phases–solid, liquid and gas using the classical laws of motion and the forces, velocities and positions of particles. Simulations were performed with at least 5000 atoms (125 ion pairs) at 298, 400, 450, 500, and 600 K. The main purpose of these simulations is the study of quantities such as the mean square displacement, traort coefficients, and the radial distribution function. Various thermodynamic quantities such as density, molar volume, thermal expansion coefficient, heat capacity at constant pressure, the molar enthalpy of vaporization and cohesive energy density were also calculated. The diffusion coefficients of ions are calculated from the slope of mean square displacement plots, the electrical conductivity from the Nernst-Einstein formulas, and the viscosity from the Stokes-Einstein relation. Simulation results are in agreement with experiment in predicting relative trends of traort properties and determining the role of the cation structure on the dynamical and traort behavior of this family of ionic liquids. Radial distribution functions of different atomic sites were calculated at 400 K. In all performed simulations via DL-POLY 2.18 software, pressure, time step, and cutoff distance were fixed at 1 atm, 0.001 ps and 16.5 ?, respectively. For each ionic liquid, all simulations were performed in the isothermal–isobaric ensemble at five different temperatures during 5 ns to reach the equilibration of the system. To calculate the properties which are mentioned above, each of the equilibrated system was studied in the isothermal–isobaric ensemble with the long simulation run for 7.5 ns (7,500,000 time steps).