Ground state properties of fluorine from DFT-hybrid functional

The ground state properties of Calcium Fluorine (CaF2), such as structural, mechanical, optical, electronic and bonding properties, have been investigated by means of density functional theory (DFT). To overcome the important underestimation of the fluorine band gap evaluated from traditional DFT functional, we use here the hybrid exchange technique mixing DFT functionals and Hartree-Fock exchange through Heyd–Scuseria–Ernzerhof (HSE06) functional. The obtained results show good agreement with experimental data using HSE06 functional. Band structure and density of states (DOS) are given and the contributions of Calcium and Fluor atoms to DOS are analysed and compared to theoretical and experimental data. Based on the dielectric function calculations over the photon energy region up to 50eV, the hybrid functional was found to accurately reproduce the optical properties of CaF2. This provides a relatively inexpensive method to describe with high accuracy the behaviour of the fluorine system with respect to its electronic and optical properties. However, the structural and mechanical properties were underestimated and overestimated respectively using HSE06 functional, the best results were obtained using GGA-AM05 functional.