Abstract
Isopropyl ammonium chloroplatinate (C3H7NH3)2PtCl6 and the corresponding chlorostannate (C3H7NH3)2SnCl6 are demonstrated to be ferroelastic by observation of the stress‐induced motion of (100) and (001) shear domain walls. The ferroelastic transition temperatures are at 37 and 40 °C, respectively, at room pressure and increase approximately linearly with increasing hydrostatic pressure. X‐ray structure analysis and the absence of measurable second‐harmonic generation (SHG) in either higher‐ or lower‐temperature phases suggest that these crystals belong to the Aizu ferroelastic species mmmF2/m.