The powder patterns were recorded with monochromatized CuKa1 radiation from capillary samples to avoid preferred orientation of the plate-like crystals. The patterns are limited to a diffraction angle of 37 °2theta since usually only little information can be deduced from higher angle reflections.
Because HLSs often show characteristic anisotropic peak broadening, this database presents for better comparison predominantly experimental XRD powder patterns and not the calculated ones. Only in those cases where no material was available the XRD patterns were calculated based on the structure data and assuming CuKa1 radiation.
The fact that the powder XRD patterns of the HLSs show anisotropic broadening of the peak halfwidths is mainly due to a certain degree of disorder of the layer stacking and to a much lesser extent to the specific morphology (thin plateletts). Typically, all reflections representing the atomic arrangement within the layer are sharp. These are the HK0-reflections, if we assume that the stacking direction is parallel to the c axis. Usuallly, all 00L-reflections representing the interlayer distance are moderately sharp (in spite of the very small crystal size along this direction), indicating that the inter-layer distances are about identical. In contrast, all other H0L, 0KL and HKL reflections with H, K, L ≠ 0 are broad. These reflections include also information on the orientation of layers relative to each other which is not perfect because only weak bonding interactions exist between neighboring layers.
Please note, that H-RUB-18 and MCM-22(p) are highly disordered materials, the listed values for the diffraction angles and intensities are not very reliable.
