Over the decades, ionic liquids (ILs) have been used as potential solvents to extract various metal ions via solvent extraction. ILs have unique physicochemical properties, such as low vapor pressure, low melting point, non-flammability, and high recyclability, and thus are considered "green" solvents. They can dissolve solutes that are weakly polar to polar and can act as a good alternative to organic solvents. The ILs mainly consist of an organic cation (e.g., alkyl-imidazolium derivatives (MMI + ), Figure ) and an anionic counterpart (e.g., PF6 -in Figure ), and the proper selection of the cation and anion determine the hydrophilic/hydrophobic nature of the ILs. The imidazolium-based ILs with hydrophobic anionic counterparts, such as PF6 -or (CF3SO2)2N -, form distinct layers with water, which helps to separate the REEs from the parent materials via liquid-liquid extraction. Besides their use in extraction, ILs are now becoming important industrial substances because of their usefulness in nuclear fuel reprocessing. They solvate the uranyl complexes and stabilize the unusual oxidation states of lanthanides. Several experimental studies focus on the extraction of REEs using ILs; however, there are fewer theoretical studies for the extraction of REEs with ILs either as extractants or as dilutants. Chaumont et al. used classical Molecular Dynamics (MD) to investigate the solvation of Ln 3+ cations, where Ln = La, Eu, and Yb, in two different imidazolium-based room-temperature ionic-liquids (RTILs) with PF6 -and AlCl4 -as the counter anions. Depending on the size of the metal ions, the coordination numbers (CN) of PF6 -and AlCl4 -around the metal ions in the first coordination shell vary.