The stoichiometric amounts of synthesized MAI (0.6734 g) and SnI 4 (1.3266 g) were mixed and enclosed in an evacuated silica ampule (P = 10 mTorr). The mixture was heated to 220 °C over 10 minutes and maintained at 220 °C for 60 hours before cooling to ambient temperature in the muffle furnace. The sample was ground and prepared on a zero-diffraction Si wafer in the air. Laboratory X-ray diffraction data were obtained using Cu Kα radiation and a Lynxeye XE-T position-sensitive detector, revealing the expected product (CH 3 NH 3 ) 2 SnI 6 .