First-principles study of the optical properties of PbFX (X = Cl, Br, I) compounds in its matlockite-type structure
We present the results of the ab initio theoretical study of the optical properties for PbFX (X = Cl, Br, I) compounds in its matlockite-type structure using the full potential linearized augmented plane wave (FP-LAPW) method as implemented in the WIEN2K code. We employed 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 Z resulting in a direct energy gap. We present calculations of the frequency-dependent complex dielectric function ε( ω) and its zero-frequency limit ε1 ( 0 ). We find that the values of ε1 ( 0 ) increases with decreasing the energy gap. The reflectivity spectra and absorption coefficient has been calculated and compared with the available experimental data. The optical properties are analyzed and the origin of some of the peaks in the spectra is discussed in terms of the calculated electronic structure.
PACS.61.50.Ks Crystallographic aspects of phase transformations; pressure effects 71.18.+y Fermi surface: calculations and measurements; effective mass, g factor 71.15.Mb Density functional theory, local density approximation, gradient and other corrections 71.15.Nc Total energy and cohesive energy calculations
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