Structure and dynamics of Co2+ in liquid ammonia: ab initio QM/MM molecular dynamics simulation

An ab initio quantum mechanical/molecular mechanical molecular dynamics simulation has been performed to describe structural and dynamical properties of solvated Co2+ in liquid ammonia. The first solvation shell was treated by ab initio quantum mechanics at unrestricted Hartree Fock level using double-ζ basis set with polarization function for Co2+ and ammonia. A newly constructed three-body corrected potential function was used for the remaining system. The stable first solvation shell forms a well-structured octahedron with a Co-N distance of 2.22 A and showed no ligand exchange process within a simulation time of 20 ps. The force constant of 39 N m-1 for the ion-nitrogen vibration indicates a weak but distinct bonding of the ligands. A mean residence time of 28.5 ps was observed for second solvation shell ligands, indicating a rather labile second coordination shell