Optical properties of the alkaline-earth fluorohalides matlockite-type structure SrFX (X = Cl, Br, I) compounds

The optical properties of the SrFX (X = Cl, Br, I) compound have been reported using the full potential linearized augmented plane wave (FP-LAPW) method as implemented in the WIEN2K code. We employed the generalized gradient approximation (GGA), which is based on exchange-correlation energy optimization to calculate the total energy. Also we have used the Engel-Vosko GGA formalism, which optimizes the corresponding potential for band structure calculations. Our calculations show that the valence band maximum (VBM) and conduction band minimum (CBM) are located at F resulting in a direct energy gap. We present calculations of the frequency-dependent complex dielectric function epsilon(omega) and its zero-frequency limit epsilon(1)(0). We find that the value of epsilon(1)(0) increases on decreasing the energy gap. The reflectivity spectra and absorption coefficient have been calculated and compared with the available experimental data. (C) 2007 Elsevier B.V. All rights reserved.