First-principles calculations to investigate electronic structure and optical properties of 2D MgCl2 monolayer

Abstract

In the present work, we have concentrated on the structural, electronic, and optical properties of single-layer phase MgCl₂. When bulk MgCl₂ reduces to monolayer form, then it exhibited indirect to direct bandgap transformation. The result indicates that the monolayer MgCl₂ exhibits insulating characteristics with a direct bandgap of 7.377 eV whereas its bulk form has an indirect bandgap of 7.02 eV. It means that when reducing the dimensionally of the MgCl₂ materials than its bandgap significantly increased. The optical properties of the monolayer MgCl₂ have been investigated using DFT within the random phase approximation. The calculated refractive index values are very near to water, which means that monolayer MgCl₂ material will be a transparent material. Also, the optical absorption coefficient is found to be very high in the ultraviolet (UV) region. From optical properties, the out-of-plane (E⊥Z) direction of polarizations is shifted towards the higher photon energy as compared to the in-plane (E||X) direction. From the optical properties profile, the polarizations along in-plane and out-of-plane are different therefore it shows anisotropic behavior. These investigated results show the monolayer MgCl₂ could be a promising material for optoelectronic nanodevices such as deep UV emitters and detectors, electrical insulators, atomically thin coating materials.