INFLUENCE OF HYDROSTATIC PRESSURE ON THE FUNDAMENTAL ABSORPTION EDGE OF TlGaSe2, TlGaS2, AND TlInS2 CRYSTALS.

The influence of hydrostatic pressure up to 1. 3 GPa on the fundamental absorption edge of TlGaSe//2, TlGaS//2, and TlInS//2 crystals is investigated. It is found that the behavior of the fundamental absorption edge of TlGaSe//2, TlGaS//2, and TlInS//2 crystals with pressure can be explained in the framework of the hypothesis about the presence of phase transitions in the pressure range 0. 3 to 0. 9 GPa. The presence of phase transitions in TlGaSe//2 and TlGaS//2 crystals agrees with the data of Raman scattering in these crystals under hydrostatic pressure.