Mapping and Characterization of Local Structures of CsPbBr.

Inorganic perovskite CsPbBr is a promising material for optoelectronic applications and high-energy radiation detection due to its excellent photophysical properties, high carrier mobility, large carrier diffusion length, and higher stability than organic perovskite materials. Understanding phase transitions at the atomic level is crucial for optimizing its applications. Here, we employ experimental characterizations and molecular dynamics simulations to study the phase transitions in CsPbBr as a function of temperature. The simulation results are compared with the experimental results, which include X-ray diffraction (XRD). Our simulations provide new insights into the electronic structure and dynamic behavior of the Cs, Pb, and Br atoms as a function of temperature. We observe distinct phase transitions from monoclinic to cubic and analyze the associated changes in the local environment through atomic density contour maps. Our analysis of the atomic density distributions of the Pb, Br, and Cs atoms provides information about the crystal symmetry as a function of temperature. The tilt and rotation angles of [PbBr] octahedra are increasing with the temperature increase and are found nonzero above 410 K when the structure is cubic, exhibiting the presence of dynamic tilting. Overall, our findings shed light on the thermal stability and structural dynamics of CsPbBr, contribute to the fundamental understanding of its phase behavior, and provide a crucial pivot for guiding the design of next-generation optoelectronic and radiation detection devices.