The electronic properties of the $1T$ phase of $\mathrm{Ti}{X}_2$ $(X=\mathrm{S},$ Se, and Te) compounds are calculated using the full potential linear augmented plane wave method as embodied in the WIEN97 code. Our calculations show that all the compounds are semimetallic. The density of states at the Fermi energy ${N(E}_{\mathrm{F}}),$ controlled by the overlap between the Ti $d$ and $Xp$ states, increases from 0.35 to 0.9 to 1.6 states/eV unit cell as we go from S to Se to Te. We report calculations of the anisotropic frequency-dependent optical properties of these compounds and find excellent agreement with the available experimental data. The optical properties show three main structures that can be attributed to transitions between the $Xp$ states and the Ti $d$ states.

• Received 21 February 2003

DOI:https://doi.org/10.1103/PhysRevB.68.245113