Polarization effects in ionic systems from first principles

A classical application of the Car-Parrinello method in the computer simulation of ionic systems is demonstrated. The induction effects in the interionic interactions are included in addition to the short-range repulsion and dispersion effects described by effective pair potentials. By representing the induced dipoles as a pair of dynamically variable charges fixed on the ends of a rod and extending the Lagrangian accordingly, the self-consistent induced dipoles at each time step are generated from the values at the previous time step, without the need for explicit minimization. Coulomb-field-induced and overlap-induced polarization effects are included and these are parameterized by ab initio electronic structure calculations. For simple ionic systems it is shown that the neglect of the overlap-induced dipoles leads to a poor representation of real systems.