Shape change as an indicator of mechanism in the high-pressure structural transformations of CdSe nanocrystals

X-ray diffraction was used to monitor the structure of 45 Angstrom diameter CdSe nanocrystals as they transformed repeatedly between fourfold and sixfold coordinated crystal structures. Simulations of the diffraction patterns reveal that a shape change occurs as the crystals transform. They also show that stacking faults are generated in the transition from the high- to the low-pressure phase. The shape change and stacking fault generation place significant constraints on the possible microscopic mechanism of the phase transition.