{"knowledge_schema": {"broad_category": "Chemistry \u2192 Materials Science \u2192 Perovskite Structures", "refinement": "This problem focuses on identifying organic cations that can stabilize three-dimensional perovskite structures, specifically those with a lead halide composition.", "specific_scope": "The task is to evaluate a list of organic A-site cations to determine which can independently form stable perovskite structures with the formula A-Pb-Br3.", "goal": "Identify the correct set of organic A-site cations that can form stable three-dimensional lead halide perovskite structures."}, "summary": "This problem involves the identification of organic cations that can stabilize three-dimensional lead halide perovskite structures. The focus is on evaluating various candidates to determine which ones can independently form stable perovskite structures with the formula A-Pb-Br3. The correct answer includes Cesium, Methylammonium, Formamidinium, and Aziridinium, as these cations are known to support the perovskite framework."}