Determination of Extraframework Cation Positions and Their Occupancies on Heulandite (010) by Atomic Force Microscopy

Atomic images of a cleaved heulandite (010) surface were obtained under an aqueous condition by atomic force microscopy (AFM). In addition to the framework oxygen atoms on the (010) plane, extraframework cations on the surface were also imaged. An AFM imaging simulation was performed using published X-ray diffraction data to assist the assignment of the AFM-observed framework and extraframework atoms. By comparing it with the observed AFM images, local variations of position and occupancy of individual cations were determined.