Molecular Dynamics Simulation Study of the Plastic/Ferroelectric Crystal Quinuclidinium Perrhenate

The structures and dynamics of quinuclidinium perrhenate, which is the first example of a plastic/ferroelectric crystal, were investigated by molecular dynamics simulation. Our simulation results showed that the quinuclidinium dipole orientations in the ferroelectric intermediate temperature phase (ITP) were preferentially distributed around three anisotropic orientations and dynamically jumped among them, which is distinctly different from the isotropic distribution and rotation of the high-temperature plastic crystal phase. We also found that the simulated temperature range of the ferroelectric ITP shrank and finally disappeared with the weakening of the hydrogen-bond interactions. These results imply that the appearance of the ITP crucially depends on the balance and competition between hydrogen-bond interactions and thermal disorder.