Numerical investigation of the electronic and optical properties of LiLuF4 vacuum ultraviolet material

Abstract

The electronic band structure and optical properties of a perfect LiLuF4 crystal were calculated using density functional theory within the projector-augmented wave method and a hybrid exchange-correlation functional. LiLuF4 is found to have a direct band gap of 10.55 eV, which is attributed to the transition between the F 2p and Li 3s bands. The dominant absorption peak originates from transitions between the F 2p to Lu 6d states and therefore, efficient emission in the vacuum ultraviolet (VUV) region is expected from LiLuF4 by exciting into the Lu 6d states using 15.21 eV (82 nm) of pump energy. The LiLuF4 crystal is highly transparent with a transmission edge of 10.37 eV (119 nm). Moreover, it is optically isotropic down to the transmission edge. Optical isotropy and transparency are desirable in the development of optical components for VUV applications, whereas the direct band gap transition is essential for efficient VUV light emission.