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 TiX2 (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 TiS2 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 TiSe2 and TiTe2 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 ε1 and ε2, 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 TiX2 (X= S, Se, Te), suggesting their potential application as a good coating material.