Molecular Dynamics Simulation of Heavy Metal Ions in Aqueous Solution Using Lennard-Jones 12-6 Potential

The dynamic and structural properties of some heavy metal ions, such as Cd²⁺, Ni²⁺, and Zn²⁺ solved in water, were studied using molecular dynamics (MD) simulation. In this paper, the radial distribution function (RDF) and self-diffusion coefficient were determined and compared with the experimental data. The results showed that the surrounding water molecules around the metal ions form a shell-like arrangement. The number of water molecules contributing in this arrangement (N_c) for Ni²⁺, Cd²⁺, and Zn²⁺ were, respectively, 8.8, 7.4, and 6. Noticeable differences between the simulation results and experimental data were observed for the nickel ion structural properties when the MM2 Lennard-Jones parameters were used to predict the interaction of nickel and water molecules. To resolve this problem, the new Ni²⁺-water Lennard-Jones interaction parameters were used in the MD simulation program to predict the structural properties of Ni²⁺ solution, which gave acceptable results.