Structural analyses of sodium cations embedded within zeolitic nanocavities

Abstract Electron microscopy combined with theoretical calculations was applied for the precise analysis of countercations within zeolitic nanocavities. We observed a light element (Na + ) within an LTA type zeolite under low dose conditions. The aberration-corrected high-resolution transmission electron microscopy (AC-HRTEM) mode has high sensitivity for small undulations in atomic potentials within a crystalline specimen. Two types of Na + were distinguishably imaged by AC-HRTEM. Delocalized Na + within an eight-membered ring (8MR) of LTA type zeolite could be imaged as a torus shape. Ab initio molecular dynamics simulations supported such delocalization of the Na + . In contrast to Na + , Cs + was located at the center of the 8MR because of its cationic size and the inner spacing of the 8MR.