This study explores the structural, mechanical, and optoelectronic properties of lead-free double perovskites K2B'AgBr6 (B' = Al, Ga, In) using density functional theory (DFT) with the modified Becke-Johnson (mBJ) exchange potential. The research focuses on the impact of trivalent cation substitutions (Al, Ga, In) at the B'-site, revealing their significant roles in fine-tuning band gaps, mechanical stability, and optical responses. The calculated band gaps range from 0.09 eV to 2.57 eV, making these materials suitable for diverse optoelectronic applications, including solar energy harvesting. Mechanical properties such as elastic constants, bulk modulus, and Debye temperature, confirm the structural robustness of these compounds for industrial use. Notably, K2GaAgBr6 exhibits a rare metallic character with intra-band transitions, highlighting its potential for advanced optoelectronic devices. This study contributes to the development of environmentally friendly alternatives to lead-based perovskites and provides insights for optimizing lead-free materials for sustainable and efficient applications.

This study employs density functional theory (DFT) to investigate the optical, electronic, mechanical, and structural properties of lead-free double perovskites, specifically Rb2B'AgBr6 (B' = Ga, Al, In). The findings indicate that Rb2B'AgBr6 compounds exhibit remarkable stability, demonstrated by their highly negative formation energies and favorable mechanical properties, including high ductility and isotropic behavior. Band structure analysis, performed using the modified Becke-Johnson potential, reveals tunable semiconducting behavior. Among the compounds, Rb2B'AgBr6with B' = Ga displays a larger band gap (3.07 eV), making it suitable for UV-visible applications, while the narrower band gap (1.90 eV) observed for B' = In suggests suitability for infrared optoelectronic applications. So Rb2AlAgBr6 has a band gap of 3.07 eV, suitable for UV-visible applications, and Rb2InAgBr6, with a 1.90 eV band gap, is suitable for infrared applications.Optical analysis shows strong absorption in the visible spectrum, highlighting the potential of these materials for solar energy devices. These results underscore the promise of Rb2B'AgBr6 compounds as lead-free, sustainable alternatives for optoelectronic applications, supporting advancements in green energy technology. Future experimental validation and exploration of dopants could further enhance device performance based on these theoretical insights. Novelty Statement: This study presents a thorough investigation of the mechanical and optoelectronic properties of Rb2B'AgBr6 double perovskites through a DFT framework, distinguishing itself by identifying Rb2AlAgBr6 as the most mechanically robust and stable configuration among the studied compounds. The research highlights the unique tunability of the band gap, facilitating targeted applications in both visible and infrared optoelectronics. Additionally, the emphasis on lead-free materials addresses pressing environmental concerns, positioning Rb-based double perovskites as innovative candidates in the quest for sustainable and efficient energy solutions. The comprehensive analysis of structural, electronic, and optical properties offers a foundation for future experimental work and further optimization of these materials in practical applications.

In the present manuscript, we report a systematic investigation of the structural, electronic, and optical properties including the elastic behaviour of erlichmanite (OsS2), using FP-LAPW method. The effect of exchange correlation functional when treated with GGA, this ductile semiconductor shows an electronic band gap of 0.34 eV that has been enhanced to 0.75 eV when mBJ potential is employed. The band gap of OsS2 further widens when Os site is doped with Fe/Ru with its highest value of 1.83 eV when 75 % of Os is replaced with Fe. The addition of dopant also improves the refractive index of the sample with highest amplitude when 75 % Fe doping and the optical absorption coefficient reaches its highest limit of 8.7 x 105 cm- 1 and 9.1 x 106 cm- 1 in the visible energy range for 75 % Fe and Ru doping, respectively.

The CuAlxGa1-xTe2 powders used in this study were made by planetary ball milling the source element powders (Cu, Al, Ga and Te). All of the produced powders and thin films were polycrystalline, with a tetragonal chalcopyrite structure with (112) orientation, according to XRD analysis. The structural and electronic features of the CuAlxGa1-xTe2 semiconductors were predicted using ab initio calculations based on Density Function Theory (DFT). The acquired results demonstrated that once the Al concentration increased, the lattice parameters and energy band gap changed in a way that was consistent with the experimental data.

Based on density functional theory, the first-principles calculations are carried out to study the optoelectronic properties of CdSe2 under hydrostatic pressure. The GGA calculation predicts the energy band gap of 0.546 eV that has been enhanced to 1.473 eV due to the inclusion of mBJ functional in the study. The current theoretical calculations present semiconductor to metal transitions at 5.1 GPa for GGA and 8.1 GPa for mBJ functional. The application of pressure (10 GPa and -8 GPa) has also successfully reproduced better optical responses like refractive index, reflectivity, and optical conductivity with an enhanced absorption coefficient of 4.867 x 105 cm-1. Their optical and electronic properties are of particular interest and suitable for applications in optoelectronics as photovoltaic devices, light emitters, and detectors.

We present an experimental and theoretical study of the perovskite-graphene nanocomposites LaFeO3 - rGO, where we demonstrate a easy way to prepare this compound using citrate auto-compulsion method, starting from corresponding metal nitrate and graphene oxide solution. The Hummer's method was used to prepare graphene oxide by chemical exfoliation of graphite. The structural characterization has been performed using XRD, FT-IR and scanning electron microscope (SEM) to analyze the morphology of the sample, FT-IR, whereas the magnetic properties has been studied using VSM measurements. Furthermore, ab-initio calculations has been performed based on the Density Functional Theory (DFT), where for a better description of the electronic and magnetic properties, the Hubbard correction was considered over the General Gradient Approximation (GGA + U).

Study of half-metallicity has been performed in a new series of Mn(2)ScZ (Z = Si, Ge and Sn) full Heusler alloys using density functional theory with the calculation and implementation of a Hubbard correction term (U). Volume optimization in magnetic and non-magnetic phases for both the Cu2MnAl and Hg2CuTi type structures was done to predict the stable ground state configuration. The stability was determined by calculating their formation energy as well as from elastic constants under ambient conditions. A half-metal is predicted for Mn2ScSi and Mn2ScGe with a narrow band gap in the minority spin whereas Mn2ScSn shows a metallic nature. The magnetic moments of Mn and Sc are coupled in opposite directions with different strengths indicating that the ferrimagnetic order and the total magnetic moment per formula unit for half-metals follows the Slater Pauling rule. And a strong effect was shown by the size of the Z element in the electronic and magnetic properties.

The electronic and magnetic properties of Mn2ZnSi(1-x)Gex (x = 0.0, 0.125, 0.25, 0.375, 0.5, 0.625, 0.75, 0.875, and 1.0) inverse Heusler alloys and Mn2ZnSi/Mn2ZnGe superlattice have been investigated using first-principles calculations. All these alloys are stable in the fcc magnetic phase and satisfies the mechanical and thermal stability conditions as determined from the elastic constants and negative formation energy. The spin-polarized electronic band structures and the density of states indicate half-metallicity with 100% spin polarization at the Fermi energy level for x = 0.0, 0.125, 0.25, 0.50, and 1.0, with the integral values of the total magnetic moments per formula unit at their equilibrium lattice constants, following the Slater-Pauling rule. The electronic properties and the magnetic moments are mostly contributed by two Mn atoms and are coupled anti-parallel to each other, making them ferrimagnetic in nature. The presence of the half-metallic bandgap with an antiparallel alignment of Mn atoms makes these Heusler alloys a potential candidate for spintronic applications.

We first performed a pure spin-polarized calculation on Nd2Fe14B using the self-consistent Full Potential Linearized Augmented Plane Wave (FPLAPW). The total charge density and the spin density calculated by taking the sum or the difference of spin-up and spin-down charge densities, respectively. In this paper, we present the spin and charge density contours for rare-earth transition metal compounds e.g. Nd2Fe14B in the (001) and (110) planes using spin-polarized only. The charge density map and the spin density map on the (001) and (110) plane of the tetragonal cell show the evidence for covalent bonding between Fe and B atoms.

The study of Cr2O3 magneto-electric material, particularly, the profound understanding of its antiferro-magnetic, is vital for its spintronics applications. In this paper, we present a study on electronic and magnetic properties of Cr2O3 crystal using the first-principles calculations based on the density functional theory. For more accurate results, additional Hubbard (U) parameter has been employed to GGA as well. Our calculated results are homogeneous with available experimental measurements. Results show the effects produced by GGA+U method upon the electronic and magnetic features of the material. We prove that, the spherically symmetric GGA+U approach for exchange correlation approximation portray is a superior depiction of electronic and magnetic properties of Cr2O3.

We have investigated the semiconducting and piezoelectric properties of bulk MNiSn (M=Ti, Zr, Hf) type a half-Heusler compound with cubic F-43m symmetry by means of density functional theory (DFT). For electron exchange correlation a generalized gradient approximation (GGA) was used. Special attention was paid to establish a most favourble ground state configuration on magnetic as well as non-magnetic ordering. With fully optimized structure the electronic and ferroelectric calculation was performed. The formation of band gap was discussed on the basis of d-d orbital hybridization. Further we have calculated the spontaneous polarization by means of structural deformation.

The calculations on electronic structures of Nd2Fe14B are calculated using first-principles full-potential linearized augmented plane wave (FPLAPW) method. We study the magnetic properties of Nd2Fe14B using the LDA+U and spin-orbit coupling methods. Results are presented for total density of states (DOS) as well as the site-projected partial density of states (PDOS) and the spin magnetic moment of Fe at each of the six in-equivalent transition-metal sites. The total spin-magnetic moments and the average Fe moment are in a good agreement with the values deduced from the neutron scattering experiment. The spin-polarized calculations, excluding the Hubbard and SO interaction, resulted in the total spin magnetic moment is 46.6 mu(B) compared to the experimental values 34.63 mu(B) to the value of 39.6 mu(B) we obtained using LDA+U scheme without Spin-Orbit coupling(SO). But using LDA+U +SO the total spin magnetic moment is 37.6 mu(B).

The electronic structures of Nd2Fe14B are calculated using first-principles fullpotential linearized augmented plane wave (FPLAPW) method. We study the effect of considering the spin–orbit coupling and Coulomb correlations in the Nd2Fe14B on the magnetic properties and the electronic structure. Results are presented for total density of states (DOS) as well as the site-projected partial density of states (PDOS), the spin magnetic moment of Fe at each of the six in-equivalent transition-metal sites and charge-spin density maps. The total spin-magnetic moments and the average Fe moment are in a good agreement with the values deduced from the neutron scattering experiment and the LDA + U + SO scheme is used. The spin-polarized calculations, excluding the Hubbard and SO interaction, resulted in the total spin magnetic moment is 46.6 μB compared to the experimental values 34.63 μB to the value of 39.6 μB we obtained using LDA+U scheme without Spin-Orbit coupling(SO). But using LDA+U +SO the total spin magnetic moment is 37.6. Including the spin-orbit coupling are necessary for getting a better agreement with experimental data. The charge density map and the spin density maps are calculated on the basal and (110) plane of the tetragonal cell. Introduction The discovered Nd2Fe14B has great interest for significant technological applications [1].It has considered a good permanent magnet because it have a large saturation magnetization , larger energy products ,coercivity and high curie temperature[2] . These compounds have complex tetragonal structures with 68 atoms per unit cell .And the fundamental role in the determining the magnetic properties are a good understanding of the electronic structure of these materials. So it is necessary to understand the origin of magnetism in Nd2Fe14B. Nd2Fe14B is the most important alloy in the series in terms of practical applications and is the one most intensively

We present first-principles calculations on SmCo5 using the self-consistent full-potential linearized augmented plane wave (FPLAPW) method. We systematically study the effect of considering the spin–orbit coupling and Coulomb correlations in the Sm f shell on the magnetic properties, electronic structure and spin-density maps. The calculated magnetic moment and magnetocrystalline anisotropy are in good agreement with experimental values when the LDA+U+SO scheme is used. This confirms the adequacy of using this scheme in SmCo5. The spin-density maps in the (001) plane show that the effect of the spin–orbit coupling on the spin-density structure of Sm atoms is stronger than that of Coulomb correlation. The reverse however, is true for Co atoms. We also study the influence of the magnetization direction on the energy bands through comparing the features of band structure when magnetization direction is along or perpendicular to the c-axis.