Ferroelasticity of TlInS2 crystal

The studies of dielectric and optical properties of TlInS2 single crystal were carried out in the temperature interval 150-300 K and in the hydrostatic pressure range up to 700 MPa. The presence of the structure of ferroelastic domains at high pressures enables us to claim that the high-pressure phase in the TlInS2 crystal is a ferroelastic one. The transition to this phase with increasing pressure is achieved via a sequence of two first-order phase transitions with an intermediate phase. A number of features are revealed in the polycritical region in the range of pressures 550-650 MPa and temperatures 180-220 K. Thus, the (p,T) phase diagram of the TlInS2 crystal in the pressure range p>550MPa is redetermined.