Lattice Dynamics of Mixed Crystals of TiSe₂

Authors

Roger D. Kirby, University of Nebraska-LincolnFollow
G.A. Freund, Jr., University of Nebraska - Lincoln

Date of this Version

December 1984

Comments

Published Phys. Rev. B. 30, 7122 (1984). Permission to use.

Abstract

We present the results of Raman scattering measurements on the mixed-crystal systems TiSe_2-xS_x, TiSe_2-xTe_x, Zr_xTi_1-x Se₂. At room temperature with the pure compounds all have crystal structures represented by the D_3d(P3̃m1) space group with three atoms per unit cell. There are two Raman-active k=0 phonons, one of A_1gˉ symmetry and one of E_g symmetry. In the TiSe_2-xTe_x system, the A_1gˉ and E_gˉ phonon frequencies shift smoothly with concentration, and the shifts are well described by a simple virtual-crystal model. The other two systems exhibit a two-mode behavior for which the virtual-crystal model does not correctly predict the observed frequency shifts. A random element isodisplacement model, based on Jaswal’s model for the pure-crystal lattice dynamics of TiSe₂ is developed. This model correctly predicts several features of the observed Raman spectra with no adjustable parameters.