Visualization of conduction channels and the dynamics of ion transport in superionic conductors

A method for visualizing conduction channels is proposed. This method is based on graphical analysis of conduction channel fragments which belong to a Voronoi-Dirichlet elementary polyhedron and lie outside the rigid sphere centered at a fixed-sublattice ion that is located at the geometric center of the elementary polyhedron under consideration. Taking into account the weak nonrigidity of spheres and root-mean-square displacements of ions in the fixed sublattice makes it possible to construct a channel as the surface of the mobile ion density. The most probable regions of mobile ion motion are quantum-mechanically interpreted as channel walls, which is confirmed by constructing the equipotential surfaces of interionic potential for α-AgI. It is found that the Andersson mathematical dynamics and the dynamics of ion transport in AgI lead to the same pattern of the motion. The symmetry rules are used for predicting the directions of motion along the allowed vibrational coordinates of tetrahedral and octahedral α-CuI fragments.