Materials that have a large unit cell with large open space such as zeolites and meso-porous silica are often used as filters, sensors, catalysts, drug delivery devices, etc. because of their cage like crystal structures. X-ray diffraction is one of the techniques often used to study those structures. One of the challenges to study structures with large unit cells is that they tend to have diffraction peaks at very low angle and it can be difficult to separate them from the direct X-ray beam coming from the X-ray source. Using a theta-compensation variable slit is one of the effective ways to reduce the direct beam scattering and resolve low angle diffraction peaks.
Figure 1 shows diffraction patterns of MCM-41 meso-porous silica and Ag behenate. The data were collected on the MiniFlex benchtop system with standard slit configuration and show excellent separation of low angle peaks which allows unit cell and lattice spacing analysis of those materials.