Ab initio and experimental study of vibrational properties of TlFeS$_{2}$ and TlFeSe$_{2}$ crystals

The lattice vibrational properties of TlFeS$_{2}$ and TlFeSe$_{2}$ crystals have been studied experimentally using Raman scattering (RS) and infrared reflection (IR) light, as well as theoretically using density functional theory (DFT). The complete vibrational representation, based on the analysis of the factor site symmetry, contains 12 active Raman modes and 9 IR active modes. 6 RS active and 3 IR active modes of them for TlFeS$_{2}$, and 4 RS active and 3 IR active modes for TlFeSe$_{2}$ were experimentally detected and identified.