Fundamental properties of the MgCl2 monolayer from first-principles calculations

Abstract

In this study, we investigated the fundamental properties of the MgCl₂ monolayer via first-principles calculations. Its stability was confirmed by the formation energy, phonon dispersion, ab initio molecular dynamics simulations and elastic constant calculations. The MgCl₂ monolayer exhibits insulating characteristics with a wide direct band gap of 5.90 eV. Its band gap can be modulated flexibly in a large range by applied strain and layer control and a direct–indirect band gap transition can be obtained. The band gaps of MgCl₂ nanoribbons along the y direction increase slightly with increasing ribbon width and are no more than 5.50 eV. But E_g oscillates along the x direction in a large range from 5.02 eV to 5.98 eV. The MgCl₂ nanoribbons have direct or indirect band gaps, relying on the cutting direction and the resulting edge configuration. Its absorption coefficient is extremely high in the ultraviolet region. The wide band gap, large dielectric constant and weak interfacial interaction with graphene endow the MgCl₂ monolayer as a promising substrate or dielectric material for nanodevices in sensing and catalytic applications.