Screening ionic motion in sodalite cages: A dynamical study

The dynamical evolution of protonated helium clusters inside sodalite cages (silica-sodalite and acidic sodalite) is followed via a Car-Parrinello approach. The static simulations give framework structural and electronic features that agree with previous experimental and theoretical data. The protonated helium clusters are used to screen the positive charge borne by a "naked" proton, and are intended as simplified models of the solvation sphere of H+. The action of the framework on the solvation shell of the proton is shown to be mainly due to induction-polarization or Coulombic forces, with a minor contribution of resonant energy exchange between the framework modes and the cluster oscillators. The covalent nature of the zeolitic O-H bond is determined with the aid of the bond order conservation principle