First-principles calculations to investigate Structural, electronic, and optical properties of MgF2 monolayer in 1T-phase and 2H-phase using hybrid functional

Full-potential linearized augmented plane-wave (FP-LAPW) method, in combination with the HSE06 hybrid functional, has been employed to investigate the structural, electronic, and optical properties of MgF2 monolayer in 1T- and 2H-phase. The stability is examined via phonon dispersion curves and cohesive energy. In both phases, MgF2 single layer exhibits insulator nature with energy gaps as large as 7.67(10.02) and 5.88(8.27) eV obtained by the WC(HSE06) functional, respectively. The density of states and valence charge distribution suggest ionic character of this two-dimensional (2D) material. Strain effect analyses indicate that the band gap decreases nearly linearly when switching the strain nature from compressive to tensile. Calculated dielectric function and optical properties including reflectivity, refractive index, and absorption coefficient assert the optical trans-parency in a wide energy range from infrared to ultraviolet. Results suggest that MgF2 monolayer may hold prospect to be applied in the spectroscopy and medical imaging systems.