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 app roach. The static simulations give framework structural and electronic feat ures that agree with previous experimental and theoretical data. The proton ated helium clusters are used to screen the positive charge borne by a "nak ed" proton, and are intended as simplified models of the solvation sphere o f H+. The action of the framework on the solvation shell of the proton is s hown 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. (C) 19 99 American Institute of Physics. [S0021-9606(99)70329-6].