X-ray diffraction pattern simulation for thermally treated [Zn-Al-Cl] layered double hydroxide

Thermal analyses and X-ray diffraction (XRD) were combined with refinement and simulation of the XRD patterns in order to elucidate the evolution of t he atom distribution in the interlayer domain of the [Zn-Al-Cl] layered dou ble hydroxide during heating, Rietveld refinement indicates that the struct ure is composed of [Zn1-xAlx(OH)(2)](0.33+) layers separated by water molec ules and chloride ions. Zn and Al are randomly distributed among the octahe dral positions. The OH layer sequence is -BC-CA-AB-BC-. Oxygen of water mol ecules and chloride ions, also randomly distributed, prefer positions at ab out 0.76 Angstrom of the threefold axis, The simulation of the XRD patterns shows that these positions were imposed by geometric constraints of water molecules connecting two OH groups of adjacent brucite-like layers. (C) 200 0 Academic Press.