Theoretical Investigation of Optoelectronics Properties of Titanium Dichalcogenides Materials TiX<sub>2</sub> (X=S, Se, Te) Using Quantum Espresso

Abstract

In this work, we present the results of the calculation of the electronic and optical properties of titanium dichalcogenide materials TiX 2 (X=S, Se, Te). These calculations were performed using the QUANTUM-ESPRESSO package, based on the density functional theory and the pseudopotential technique. The results obtained showed that TiS 2 is a semi-metallic compound, this character is due to a very small overlap between the density of states p-orbitals of S and d-orbitals of the Ti atom in the vicinity of the Fermi level. While TiSe 2 and TiTe 2 indicate the metallic characters. At the Fermi level, the total density of states is 0.77 states/eV and 1.13 states/eV for both compounds respectively. On the other hand, the optical properties of these materials such as the real and imaginary parts of dielectric function ε 1 and ε 2 , respectively, the refractive index, the absorption, the reflectivity, and the loss function were investigated based on Kramers-Kroning relations in the energy range of 0 to 20 eV. In the infrared region, the reflectivity spectrum R(ω) is close to 100% for TiX 2 (X= S, Se, Te), suggesting their potential application as a good coating material.