Ferroelastic domain structure of (CH3)(4)N CdCl3 (TMCC) crystal

The ferroelastic domain structure and the phase boundaries of TMCC have bee n studied in the temperature range 114-90 K by direct observation under pol arised light. By applying an external, compressive and unidirectional mecha nical stress the ferroelastic character of the domain structure has been co nfirmed. The orientation of the domain walls and phase boundaries are analy sed. To characterise quantitatively the observed domain wall distribution t he classical symmetry approach, based on the criterion of spontaneous strai n compatibility, has to be extended to allow small rotations of the domain walls with respect to their ideal orientation. The observed switching proce ss among the different domains can be understood as a mechanism that minimi ses the elastic energy.