Development of Lennard-Jones and Buckingham Potentials for Lanthanoid Ions in Water

New sets of Lennard-Jones and Buckingham potentials have been developed to be used in classical molecular dynamics simulations of Ln³⁺-containing systems for the whole lanthanoid series. The force-field parameters have been refined by directly comparing the hydration structure obtained from the simulations with the extended X-ray absorption fine structure (EXAFS) experimental data, in order to reproduce Ln³⁺-water EXAFS experimentally inferred mean distances. Analysis of the simulation results has shown that both Lennard-Jones and Buckingham potentials are able to properly describe the radial distribution of water molecules around the Ln³⁺ ions, the smooth decrease of the hydration number along the lanthanoid series, as well as the geometry of the first-shell hydration complex formed by Ln³⁺ ions in water. The newly optimized interaction potential parameters can be used in conjunction with force fields available in the literature to investigate the solvation properties of Ln³⁺ ions in different disordered systems.