Far-infrared study and lattice dynamics simulation of Cs2HgBr4 crystal

Far-infrared reflectivity investigations of Cs2HgBr4 crystal were performed in the temperature region of 10-297 K. A sequence of the phase transitions can be recognised by activation of new modes below the phase transition po ints. In order to interpret the experimental IR data at room temperature th e lattice-dynamical modelling in the framework of atomic model was carried out. Comparison of the calculated phonon frequencies with the experimental ones shows a reasonable agreement for most of them. The eigenvector analysi s is presented.