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Abstract: A first-principles technique capable of describing the state accurately near to excited states of semiconductors and insulators, namely the modified Becke-Johnson (mBJ) exchange potential approximation is used to investigate the opto-electronic response of magnesium spinel oxides: MgAl2O4 and MgGa2O4. The predicted bandgaps using the mBJ exchange approximation show a significant improvement over previous theoretical work using the common LDA and GGA, and are very closer to the experimental results. Band gap dependent optical parameters, like dielectric constant, index of refraction, reflectivity and optical conductivity are calculated and analyzed. The static dielectric constant and refractive index of MgGa2O4 are much larger than that of MgAl2O4. Refractive index drops below unity for higher energy photons, higher than 17eV, show that the velocities of incident photons are greater than the velocity of light. However, these overlook can be explained by the fact that a signal must be transmitted as a wave packet rather than monochromatic wave. Moreover, the peak positions of the calculated optical parameters move down to low energies when the value of the band gap decreases. This comprehensive theoretical study of the optoelectronic properties predicts that these materials can be effectively used in the optical devices working in major part of the spectrum. [Copyright &y& Elsevier]

Abstract: The structural, electronic and optical properties of AgTF3 (T=Mg, Zn) are calculated for the first time using the full-potential linearized augmented plane wave method within the generalized gradient approximation. Structural parameters of the compounds are found to be in reasonable agreement with the available literature. Both compounds are found to have narrow and indirect band-gaps. The calculated band gap for AgMgF3 is 0.78eV and 0.75eV for AgZnF3. It is observed that Ag-4d, Zn-3d and Ag-5s states controls the electronic properties of AgMgF3 and AgZnF3. The nature of chemical bonding in these compounds is discussed by the electron density plots. The results of complex dielectric constant, refractive index, normal-incidence reflectivity and optical conductivity are also presented in the incident photon energy range of 0–35eV. The wide absorption energy range makes these materials suitable for different devices applications. [Copyright &y& Elsevier]