Refinement of Crystal Structure of SbSI in the Ferroelectric Phase

Crystal structure analysis of SbSI in the ferroelectric phase has been made at 1.3°C by using full three-dimensional Bragg reflection data collected with X-ray automatic four-circle diffractometer. The discrepancy factor is 0.030. The atomic shifts from the positions in the paraelectric phase take place along the ferroelectric c -axis by 0.103 Å for Sb atoms and 0.019 Å for S atoms. A large thermal parameter of 0.16 Å in amplitude is seen for Sb atoms along the c -axis. The split atom method has shown that the nature of the phase transition is very close to the displacive type.