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Structural and optoelectronic properties of pure and Co doped In2O3 are studied by employing the full-potential linearized augmented plane wave method, which is known to produce highly accurate results. First principles calculations are performed with ordinary generalized gradient approximation (GGA) along with new Hubbard and modified Becke-Johnson exchange (mBJ) potential techniques. Improved band gap results are obtained for In2O3 with GGA+𝑈 and mBJ. In the case of mBJ, the band gap values are 3.5 eV and 3.4 eV for rhombohedral and cubic phases, which are in close agreement with the experimental data. Substitution of In by Co 25% alters the energy gap and a spin splitting effect is observed in these phases. For the spin-up state, it remains semiconductor, whereas for the spin-down state it shows semimetallic behavior. The value of static refractive index 𝑛(0) is 1.74 for the cubic phase, while in rhombohedral phase the values of 𝑛(0) are 1.77 and 1.74 along 𝑥𝑥 and 𝑧𝑧 optical axes, respectively. The calculated optical properties conform anisotropy in the rhombohedral phase and these materials can be potential candidates for the optoelectronics applications.

The electronical and optical properties of CdGa 2 S 4 under high pressures were studied using the full potential linearized augmented plane wave (FP-LAPW) method within the GGA and mBJ exchange correlation potentials from 0.0 to 16.92 GPa. The obtained results show that the lattice constants, bandgap values, and optoelectronic properties are sensitive to applied external pressures. The mBJ results indicate that the bandgap increases and the static dielectric con-* Dr. H. A. Rahnamaye Aliabad 839 stants decrease with increasing the pressure. The two none zero dielectric tensor components show considerable anisotropy between the perpendicular and parallel components. The maximum absorption for x direction in all pressures takes place in vacuum UV region. Also, the plasma frequency shifts to the higher energies with increasing the pressure for application in optical devices. The calculated results by mBJ are in close agreement with the experimental values.

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