Electronic structure and optical properties of In2X2O7 (XÂ =Â Si, Ge, Sn) from direct to indirect gap: An ab initio study

Electronic optical properties of In2X2O7 (X = Si, Ge, Sn) compounds were calculated using density functional theory (DFT) calculation based on full potential linear augmented plane wave (FPLAPW). Four schemes LDA, GGA, EVGGA and mBJ were used to solve exchange correlation factor. The calculations of In2X2O7 show that mBJ give better band splitting. The band structure of In2Ge2O7 show an indirect band gap (X → Г) of about 3.55 eV while In2Si2O7 and In2Sn2O7 exhibit direct band gap (Г → Г) of 5.59 eV and 2.44 eV. The frequency dependent dielectric functions of In2X2O7 compounds show the highest transparency at the infrared (IR) region. The In2Si2O7 and In2Ge2O7 are broad band semiconductors starting from ultraviolet (UV) region while In2Sn2O7 start from visible region. The reflectivity spectra shows that In2X2O7 compounds are suitable for antireflection coating layer in solar cells and filters in far UV region. As In2Si2O7 and In2Sn2O7 are a direct band gap material, that make them suitable for light emitting diodes (LED's). In2Si2O7 is suitable for UV light while In2Sn2O7 is fit to emit green, blue and violet light. The present work provides information about variation of the electronic and optical properties by replacing Si by Ge and by Sn in the pyrochlore oxide which helps to understand the electronic and optical properties of this group of compounds.