Tuning the electronic and optical properties of Co2TiGe Heuslerene by selecting Ge- or Ti- termination structure

•Phonon stability of Co2TiGe Heuslerene.•Molecular dynamic stability of Co2TiGe Heuslerene.•Half-metallic behavior of Co2TiGe Heuslerene by HSE.•Sensitive the optical response Co2TiGe Heuslerene to the light angle. In this work, the Ge- and Ti-termination monolayers of Co2TiGe were investigated by density functional theory. The phonon dispersion curves of these monolayers revealed their dynamical stability. The calculated spin-resolved density of states and band structure of the monolayers confirmed the asymmetrical pattern of spin-up and spin-down showing the magnetic as well as the half-metallic characters of these monolayers. The calculated optical properties of the Ge- and Ti-termination monolayers of Co2TiGe by the Bethe-Salpeter equation showed the absorption of Ge-termination in the visible region of the electromagnetic spectrum which was extended to the UV region in the Ti-termination monolayer.