We have synthesized Gd_2FeCrO_6 (GFCO) double perovskite which is crystallized in a monoclinic structure with P2_1/n space group. The UV-visible and photoluminescence spectroscopic analyses confirmed its direct bandgap semiconducting nature. Employing experimentally obtained structural parameters in first-principles calculation, we report the spin-polarized electronic band structure, charge carrier effective mass, density of states, electronic charge density distribution and optical absorption

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... roperty of the GFCO double perovskite. The effects of on-site d-d Coulomb interaction energy (U_eff) on the electronic and optical properties were investigated by applying a range of Hubbard U_eff parameters from 0 to 6 eV to the Fe-3d and Cr-3d orbitals within the generalized gradient approximation (GGA) and GGA+U methods. When we applied U_eff in the range of 1 to 5 eV, both the up-spin and down-spin band structures were observed to be direct. The charge carrier effective masses were also found to enhance gradually from U_eff = 1 eV to 5 eV, but, these values were anomalous for U_eff = 0 and 6 eV. These results suggest that U_eff should be limited within the range of 1 to 5 eV to calculate the structural, electronic and optical properties of GFCO double perovskite. We observed that considering U_eff = 3 eV, the theoretically calculated optical band gap 1.99 eV matched well with the experimentally obtained value 2.0 eV. The outcomes of our finding imply that the U_eff value of 3 eV most accurately localized the Fe-3d and Cr-3d orbitals of GFCO keeping the effect of self-interaction error from the other orbitals almost negligible. Therefore, we may recommend U_eff = 3 eV for first-principles calculation of the electronic and optical properties of GFCO double perovskite that might have potential in photocatalytic and related solar energy applications.