Microscopic picture of Na ion behavior in the one-dimensional tunnel of hollandite-type has been studied by molecular dynamics simulations. The characteristic distribution of Na ions determined by the X-ray study has been satisfactorily reproduced by using a two-body central-force interaction between ions. Trajectories of Na ions are characteristic and not identical to each other. Alternative occupation of Cr(III) or Ti(IV) at the framework-metal position is an important factor for the trapping of Na ions which are more attracted toward CrO6 octahedra than TiO6.
Michiue, Y., & Watanabe, M. (1996). Molecular dynamics simulation of sodium ions in one-dimensional tunnel structure of hollandite-type. Journal of Physics and Chemistry of Solids, 57(5), 547–551. https://doi.org/10.1016/0022-3697(95)00296-0