The global attempts of clean and sustainable energy solutions have strengthened the search for desirable and efficient materials for hydrogen storage. From this perspective, complex hydrides have recently emerged as suggesting candidates due to their tunable physical properties and high hydrogen content. The current study offers a computational investigation of a novel class of quaternary complex hydrides, KBaMH6 (M = Co, Rh, Ir), using density functional theory (DFT). The Structural stability of the studied materials was confirmed through phonon dispersion analysis, revealing dynamically stable cubic phases for all three compositions. Furthermore, AIMD simulations at elevated temperatures confirmed the thermal robustness of the compounds, highlighting their structural integrity during hydrogen cycling. Electronic structure analysis of KBaMH6 indicates the semiconducting nature with an indirect band gap. The optical properties of the investigated structures reveals that the hydrides strongly absorb ultraviolet (UV) light, with a obvious red shift in the absorption edge due to changes in the band gap. The computed hydrogen storage capacities for KBaCoH6, KBaRhH6, and KBaIrH6 are 2.51, 2.12, and 1.61 wt%, respectively. The results suggest that KBaMH6 hydrides, particularly with transition metals Co, Rh and Ir, represent potential candidates for next-generation solid-state hydrogen storage systems.

This work presents a first-principles investigation of cubic NaInBr3 perovskite using density functional theory (DFT) within the generalized gradient approximation (GGA). The Structural optimization of the perovskite confirms its mechanical stability, yielding a lattice constant of 5.75 Å and a bulk modulus of 18.41 GPa, indicating that the compound is mechanically soft. The electronic band structure reveals a direct band gap of ∼0.4 eV at the R point, highlighting its semiconducting nature and potential for optoelectronic applications. The density of states (DOS) shows dominant contributions from Br-4p and In-5p orbitals in the valence and conduction bands, respectively. Optical property calculations indicate a moderate static dielectric constant (ε1 (0) = 3.53), a high absorption coefficient (1.32 × 108 cm−1), and pronounced plasmonic responses, suggesting potential applications in ultraviolet photodetectors, photovoltaics, and plasmonic devices. Thermodynamic analysis demonstrates structural and thermal stability across a broad pressure range, as evidenced by increasing Debye temperature, entropy, and specific heats, along with decreasing Gibbs and vibrational free energies. The obtained results of the study establish NaInBr3 as a promising candidate for thermoelectric, ultraviolet optoelectronic, and high-temperature energy applications.

This work used density functional theory (DFT) and semiclassical Boltzmann transport calculations to investigate the structural, electronic, optical, and thermodynamic properties of the Ge-based double perovskite Rb2InGeX6 (X = Cl, Br, I). The performed calculations reveal that the three investigated structures have tunable semi-metallic behavior defined by valence band crossings at the Fermi level, with band gaps ranging from Rb2InGeCl6 (0.74 eV) > Rb2InGeBr6 (0.33 eV) > Rb2InGeI6 (~0.00 eV). The Fermi level’s Ge-P, In-P, and halide-P orbitals significantly influence the conductivity of the materials. The assessed optical properties of Rb2InGeX6 (X = Cl, Br, I) show different light–matter interaction behaviors with strong halide dependence: Rb2InGeBr6 shows notable transparency in the infrared-visible spectrum (IR), while Rb2InGeCl6 and Rb2InGeI6 show strong absorption in the NIR-visible range, implying they are appropriate for distinct photonic applications (for example, IR optoelectronics versus NIR-IR photodetectors). Furthermore, the thermodynamic investigation over a wide range of temperatures shows that halide substitution significantly affects the thermoelectric properties. Rb2InGeBr6 exhibits n-type conduction with an enhanced absolute Seebeck coefficient and high power factor, leading to a superior figure of merit (ZT) relative to the p-type Rb2InGeCl6 and ’semimetallic’ Rb2InGeI6. Notably, Rb2InGeBr6 combines a narrow band gap and infrared transparency with outstanding thermoelectric metrics. The obtained results offer a complete understanding and a new perspective on the tunability of Rb2InGeX6 perovskites for next-generation optoelectronic, photovoltaic, and energy harvesting uses.

This study investigates the structural, electronic, and optical properties of tetragonal-phase RbGeA2X (A = Br, Cl; X = Br, I) lead-free mixed halide perovskites using density functional theory (DFT) with PBE-GGA for exchange-correlation energy. These perovskites show enhanced properties, including high charge carrier mobility, tunable direct band gaps, and strong ultra-violet (UV) absorption. Band structure and density of states (DOS) analyses highlight their suitability for optoelectronic applications. Optical studies of the dielectric function and absorption coefficient of the studied structures confirm their ability to absorb electromagnetic radiation beyond the visible spectrum, making them promising candidates for advanced (UV)-range optoelectronic devices.

In this study, the structural, electronic and optical properties of cubic lead-free halide perovskites LiSnX₃ (X = Br and Cl) under hydrostatic pressure are investigated. The first-principle approach based on density functional theory (DFT) is employed. The exchange-correlation functional is treated using the generalized gradient approximation (GGA), specifically a variant of the Perdew–Burke–Ernzerhof (PBE) method. The aim of the study is to understand the effect of pressure on the properties of LiSnX₃ (X = Br and Cl), with a maximum pressure limit of 6 GPa. The results show a decreasing tendency in the energy band gap as pressure increases. In addition, a prominent reduction in the energy band gap is observed when the halogen atom is changed from Cl to Br under constant pressure. The calculations also investigate the density of states (DOS), showing variations in energy levels near the Fermi level under different pressures. For optical properties, density functional perturbation theory (DFPT) is used in conjunction with the Kramers-Kronig relation. Optical parameters such as the real and imaginary parts of the dielectric constant, refractive index, absorption coefficient, and wavelength are computed under different pressures to understand the optical response of the perovskites to the electromagnetic spectrum. The insights from this study highlight the fundamental properties of LiSnX₃ (X = Br and Cl) under different pressures, which could influence advancements in optoelectronic devices, photonic applications, and solar cell technologies. Moreover, this research contributes to the growing body of knowledge on lead-free halide perovskites, encouraging further developments in the field.

This study examines the structural, electrical, optical, and mechanical effects of hydrostatic pressure on cubic I-II-halide perovskite RbSrI3. The exchange-correlation term of the Khon-Sham equation is expressed using PBE-GGA. For all calculations, QuantumESPRESSO is used. PBE-GGA and pseudopotentials have been employed for ion-valence interaction. Under hydrostatic pressure, the lattice parameter a dropped from 6.34 Å. The structure is thermodynamically stable since the formation energy E_f is negative and lowers as the negativity falls until pressure 31 GPa, when it becomes positive. This material depicts the transition from an indirect band gap at ambient pressure to a direct band gap that accelerates electron valence-to-conduction band transition. The band gap rises to 7 GPa, then falls to 1.49 eV at 50 GPa. The PDOS explains that the states that contribute to creating VBM and CBM changes in overlapping status and value which leads to such behavior of electronic nature. Optical properties show a stronger response at 50 GPa pressure, with ε_1 (ω) and ε_2 (ω) exhibiting similar behavior and a maximum value of nearly 10. However, ε_1 (ω) peaks in the visible light zone, while ε_2 (ω) peaks in the ultraviolet zone. This means the material absorbs and retains visible and ultraviolet radiation at its optimal level. Mechanical and elastic parameters were determined using finite strain theory. Born stability confirms mechanical stability since C_11, C_44, C_11-C_12, and C_11+2C_12 have positive values and remain positive as pressure increases. Elastic moduli such bulk modulus (B), shear modulus (G), and Young's modulus (E) indicate moderate hardness and resistance to pressure. Additionally, Poisson's ratio (υ), Pugh's ratio, and Cauchy pressure (σ) indicate ductility at ambient pressure, since they align with boundary values of υ (0.2959 > 0.26), σ(0.92) (positive), and B/G (2.23 > 1.75) (at ambient pressure). Increased pressure enhances ductility.

We study structural, electronic and optical properties of inorganic lead-free halide perovskites RbGeX3 (X = Cl, Br and I) under hydrostatic pressure, which could facilitate development of new optoelectronic and solar-cell technologies. ab initio first-principles calculations are employed based on the generalized gradient approximation within the framework of density functional theory. We demonstrate that the bandgap of our perovskites decreases with increasing pressure. At a given pressure, the bandgap becomes narrower when the halogen atom is changed from Cl to I. We also examine the density of states and demonstrate that the energy levels near the Fermi level change significantly under pressure. The optical properties are calculated using the density functional perturbation theory and the Kramers–Kronig relation. The optical parameters such as the real and imaginary parts of the dielectric function, the refractive index and the absorption coefficient are calculated under different pressures.

The current research uses density functional theory (DFT) approximations in conjunction with the plane wave-pseudopotential method to investigate structural, electronic, and optical properties of Pb-free cubic perovskite RbGeX3 (X= I, Br and Cl) materials. More specifically, Norm-conserving pseudopotential has been employed to describe the ion and valence electrons interaction, and Perdew-Burke-Ernzerhof (PBE) flavor is used to represent the exchange-correlation part of the energy of the GGA approximation. Our calculated lattice constants are 5.95, 5.55, and 5.29 Å for RbGeX3 (where X=I, Br, and Cl), respectively, and they are of are in good agreement with available empirical and other values. The band structure shows the direct band gap nature of the three compounds under research here and our values of the band gap energy E_g are in good agreement with the other available results. Materials under research show response to the electromagnetic radiation starting from the infrared region to the very high energies (~33 eV). The RbGeI3 has the lowest E_g value at the low region energies and the highest optical response peaks but RbGeCl3 has the highest optical response peaks at energies located near ~20 eV. Our results show that these materials are good candidates for photo electronic applications including solar cells.

A self-consistent calculation within Density Functional Theory (DFT) using norm-conserving pseudopotential plane-wave and the precise hybrid functional HSE06 were performed. The stability, elastic, originatemechanical, electronic, and optical properties of the cubic perovskites LiGeX3 (X = Br Cl, and I) are investigated. The behaviour of the stability and elastic characteristics under hydrostatic pressure is also presented and studied. Band structure analysis using PBE, GW-Approximation, and HSE06, show that LiGeX3 (X = Br Cl, and I) are direct bandgap semiconductors. The structures are most stable at the computed relaxed lattice parameters (a=b=c=5.880,5.470and5.190Ao)for the LiGeI3, LiGeBr3, and LiGeCl3, respectively. The Pressure dependence of cubic perovskite elastic moduli, bulk modulus B, shear modulus/constant (G,Cs), Young's modulus E, the Poisson's ratio σ, Vickers hardness Hv, Lame's constants (λ,μ), Cauchy pressure C12−C44, the Anisotropy factor A, Kleinman parameter ζ, and the P-wave modulus Pw, elastic wave velocities v, Debye temperature θD is presented. The optical properties including the static refractive index and dielectric constant are found to be related to the direct bandgaps, proportionally. The refractive index, extinction coefficient, complex dielectric function, energy loss function, optical conductivity, reflectivity, and absorption coefficient for 0–25eVincident photon energies are also presented.

Plane waves with norm conserving pseudopotentials (PW-PP) method in conjunction with density functional theory (DFT) frame work have been used to investigate structural, electronic and optical properties of lead-halide cubic perovskite CsPbX3 (X=Br, Cl and I). The generalized gradient approximation (GGA), specifically Perdew-Burke-Ernzerhof (PBE) flavor, has been chosen to treat the exchange correlation term of Kohn-Sham equation. Structural parameters are comparable with other theoretical and experimental studies. In spite of good agreement of our band gap values with other theoretical works, however, they were not comparable when compared to the experimental values due to the well-known problem of Eg value underestimation of DFT. To update the value, we have used GW method as a self-consistent quasiparticle method on energies and wave functions and indeed they have been improved. Optical properties have been calculated using density functional perturbation theory (DFPT). Our results show that CsPbX3 (X=Br, Cl, I) has maximum response to the electromagnetic spectrum at low energies (visible region) but minimum response at high energies.

In the recent years, caesium lead halides CsPbX3 with the halogen elements Cl, Br and I have gained much attention of researchers owing to their attractive optical properties. In the present work we discuss the changes in their structure, bandgap and optical properties that occur under hydrostatic pressures 1–10 GPa. The density functional theory based on the generalized gradient approximation within the Perdew–Burke–Ernzerhof approach for exchange-correlation energy is used for calculations, in conjunction with the augmented plane-wave pseudopotential method. Since the generalized gradient approximation underestimates the bandgap, we employ the GW method to improve the bandgap values. The optical properties are computed in the photon-energy range 0.1–3.6 eV, using the density functional perturbation theory. As the pressure increases, the Pb–halogen bonds become contracted, whereas the volume of the unit cell shrinks uniformly, with no phase or structure-type transformations. The bandgap decreases with increasing pressure and the corresponding decrease rate for CsPbI3 is less than that for CsPbBr3. In general, the optical response of the caesium lead halides increases with increasing pressure, while the peaks of maximums of the response functions are red-shifted.

During operating of the X-ray machines, if the protection of X-ray rooms is insufficient, not only the patient but also clinical staffs as well as public are exposed to high X-ray dosage and they are affected from X-ray related to the dose level. In the present survey, by testing the radiological leakage and scatter from X-rays machines in radiology departments of 7 randomly selected hospitals in Duhok governorate, the effects dose of X-ray to the both control panel area and the patients waiting or visiting area who are located near the radiography room, were measured. The dose was recorded for a range of peak kilovoltage (kVp) and mAs values to find efficiency of shielding materials (barriers) of radiography rooms for different X-rays level. The measurements were performed at one meter above the ground surface which was the same height of X-rays tube by using Gamma Scout dosimeter. From the measurement results, it was seen that the most hospitals barriers (doors and walls) were not appropriate to the standards except 2 hospitals. The maximum effective doses were measured in uncontrolled area of Khazer hospital which was 82.48 ± 0.73 mSv·yr-1 that was much more than the reference dose limits and in controlled area of Haval Banda Zaroka hospital which was 12.98 ± 0.16 mSv·yr-1. In result, the knowledge about the radiation dose affecting the radiologists and public in the selected hospitals was obtained, and by informing the radiologists and the hospitals managements, the necessary regulations would be planned.

Pseudopotential plane wave method within local density approximation (LDA), generalized gradient approximation (GGA) frameworks and GW approximation (in conjunction with the ABINIT package) is used to investigate lattice constant parameter (ܽ) and band structure for zincblende BN and GaN. To be more specific, the Perdew-Wang92 (PW92) and Perdew-Burke-Ernzerhof (PBE) flavors have been employed for exchange-correlation term of LDA and GGA, respectively. Lattice constant (ܽ), band gap energy (ܧ (௚have been calculated using LDA and GGA approximations. The GGA results for (ܽ) are strongly agree with the experimental and much more accurate than LDA values. The values of ܽ in both LDA and GGA methods are well accurate when compared with the other theoretical works. The ܧ ௚values obtained are in a good agreement with other theoretical works especially for ZB-BN. On the other hand, the ܧ ௚values are not in good agreement with the experimental due to the well known band gap problem of density functional theory (DFT). To improve the ܧ ௚value, GW approximation has been used. It was found that the improvement is better for ZB-BN than ZB-GaN