The film shows how proton transfer in a proton-ion complex takes place in a molecular cluster. The aim of the research is to examine how reaction rates and mechanisms are modified when the solvent in which the reaction takes place is a cluster with linear dimensions in the mesoscopic range.
The proton-ion complex consists of two ions a fixed distance apart. The proton can form hydrogen bonds with either ion and the reaction consists of the transfer of the proton from one ion site to the other. The proton-ion complex is represented by the light colored sites while the two atoms in the dipolar solvent molecules are red and blue.
The first two film clips show a sequence of cluster configurations generated from a fictitious dynamics constructed from a Feynman path integral representation of the proton. The configurations reflect the equilibrium structure and are used to construct the free energy of the proton transfer process. In the first clip the proton is constrained to lie at the free energy maximum (transition state) and the cluster molecules surround the proton-ion complex in most configurations. In the second clip the proton is constrained in the reactant (or product) state where it is hydrogen bonded to one ion, and the proton ion complex is seen to "float" on the surface of the cluster in most configurations.
The third clip shows the actual dynamics computed in the adiabatic approximation.
S. Consta and R. Kapral, "Proton Transfer in Mesoscopic, Molecular Clusters", J. Chem. Phys. 101, 10908 (1994).