The rietveld structure refinement of an exceptionally pure sample of clinoptilolite from Ecuador and its Na-, K-, and Caexchanged forms

The crystal structures of a highly pure, sedimentary clinoptilolite and the Na-, K-, and Ca-exchanged forms were refined by the Rietveld method using X-ray diffraction data collected with both conventional and synchrotron sources and different instrumental geometries. The refined structures showed that the clinoptilolite framework is not sensitive to cation exchange with Na +, K + or Ca 2+. The M1 extraframework cation site is occupied by Na, Ca, and Ba, M2 by Ca, M3 by K, and M4 by Mg. The M1 site occupancy significantly influences the configuration of extraframework water molecules. © by Oldenbourg Wissenschaftsverlag, München