20062: Mashi

Authors: ^*H. Mashiyama, Y. Kawamura and Y. Kubota⁺
Affiliation: Graduate School of Science and Engineering, Yamaguchi University, Yamaguchi 753-8512, Japan
⁺ Graduate School of Science, Osaka Prefecture University, Sakai, Osaka 590-0035, Japan

The orthorhombic phase IV of MAPbBr₃ was investigated by using synchrotron X-ray diffraction data from the powdered crystal measured by using a Debye-Scherrer camera. The diffraction pattern at 115K was fitted by using a Rietveld method to refine the structural parameters. Some orthorhombic space groups, as well as monoclinic space groups, were tried to fit the data. The crystal symmetry was assigned as Pnma (Z=4), a nonpolar space group with a=7.976, b=11.841, c=8.565 A. The crystal structure of phase IV can be derived from cubic phase I, but not from the tetragonal phase II. The polar MA ions are located in an anti-parallel way to cancel the polarization. The successive transitions are discussed from the structural viewpoints.