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 > 550 MPa is redetermined.