Optical Phonons and Chemical Bonding in TlSbS2, TlSbSe2, and Tl3SbS3 Crystals

Abstract

The optical phonons at k = 0 of TlSbS2, TlSbSe2, and Tl3SbS3 have been investigated by infrared reflectivity measurements from 50 to 4000 cm−1 at 300 K. The factor group analysis of vibrational modes of TlSbS2 and Tl3SbS3 crystal lattices has been made. The dielectric constant dispersion for E ‖ a and E ‖ b has been determined by classical dispersion relations. The Szigeti effective charges, the Born dynamic effective charge, and the Tl, Sb, S (Se) relative ion charges were calculated in dependence on the polarization of the incident light.