2025-09

Physica Scripta

Density functional theory (DFT) was used to investigate the structural, electronic, optical, and thermodynamic properties of the double perovskite Rb₂InGeX₆ (X = Cl, Br, I). The performed calculations reveal that the three investigated structures have semi-metallic behavior defined by valence band crossings at the Fermi level, with band gaps ranging from Rb₂InGeCl₆ > Rb₂InGeBr₆ > Rb₂InGeI₆. The Fermi level's Ge-P, In-P, and halide-P orbitals significantly influence the conductivity of the materials. The density of states (DOS) investigations emphasize the role of individual atomic orbitals in shaping the electronic structure. The analyzed optical properties of Rb₂InGeX₆ (X = Cl, Br, I) show different light-matter interaction properties: Rb₂InGeBr₆ shows notable transparency in the infrared-visible spectrum (IR), while Rb₂InGeCl₆ shows strong absorption in the visible-UV range. Whereas Rb₂InGeCl₆ is appropriate for UV photodetectors and light-harvesting technologies, the computed refractive index and reflectivity verify the fit of Rb₂InGeBr₆ for IR photodetectors and optoelectronic devices. Furthermore, the thermodynamic calculations over a wide range of temperatures show that halide substitution significantly affects the thermoelectric properties. Rb₂InGeBr₆ exhibits n-type conduction with an enhanced absolute Seebeck coefficient and better power factor; Rb₂InGeCl₆ and Rb₂InGeI₆ present p-type behavior with more modest thermoelectric performance. 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.

2025-09

Physica Scripta

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.

2025-04

Transactions on Electrical and Electronic Materials

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.

2025-02

PLOS ONE (Issue : 2) (Volume : 20)

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.

2024-12

Semiconductor Physics, Quantum Electronics & Optoelectronics (Issue : 4) (Volume : 27)

Pseudopotentials and density functional theory (DFT) implemented in the ABINIT code were used to study the properties of the GaSb cubic alloy zinc-blende structure. Both the local density approximation and the generalized gradient approximation were used for the exchange-correlation (XC) potential calculation. The calculated lattice parameter aligns well with available experimental and theoretical results. Elastic constants, Young’s modulus, shear modulus, and anisotropy factor were determined, and the pressure dependence of elastic constants was investigated. Band gaps were initially calculated but showed discrepancies with experimental values due to the known band gap problem of DFT. To enhance accuracy, the Green function and screened Coulomb interaction approximation were introduced. The impact of thermal effects on compound properties was investigated using the quasi-harmonic Debye model, presenting variations in volume, heat capacities, thermal expansion coefficient, and Debye temperature concerning pressure and temperature.

2024-07

Indian Journal of Physics (Issue : 11) (Volume : 98)

In this study, the structural, electronic and optical properties of the tetragonal-phase of the free-lead mixed halides perovskites RbGeI2Cl and RbGeBr2Cl are investigated. These materials have raised an interest due to their enhanced electronic and optical properties, demonstrated by high charge carrier mobility and adjustable band gap. The calculations employed ab-initio methods, predominantly based on the density functional theory (DFT), the exchange– correlation functional is processed with the generalized gradient approximation (GGA) approach which uses a ‘flavour’ of the Perdew Burke Ernzerhof (PBE). The DFT framework allows to study the structural parameters, band structure, and density of states (DOS). The calculations of the band structure show that RbGeI2Cl and RbGeBr2Cl have a direct band gap. In addition, the dielectric function and absorption coefficient as part of the investigation into the optical properties of these perovskites are calculated. The obtained results suggest that the two studied mixed halide perovskites have the capability to absorb electromagnetic radiation outside the visible spectrum, making them a promising candidate for potential uses in optoelectronic applications within the ultraviolet (UV) range.

2022-12

Ukrainian Journal of Physical Optics (Issue : 1) (Volume : 23)

Inorganic halide-based perovskites are of great interest as materials for photo-voltaic and optoelectronic devices. Here we present a first-principles study of the structural, electronic, elastic and optical properties of alkali-metal lead iodides MPbI3 (M = Li, Na, K), with the emphasis on the role of their first cation M. In particular, this work is the first investigation of the elastic and optical properties of MPbI3 (M = Na, K). Our results show that the first cation has insignificant effect on the properties mentioned above, although there is some increase in the lattice constant when we pass from Li to Na. The energy band gap values calculated for our perovskites in a generalized gradient approximation agree with the available theoretical data but not with the experimental results. A better agreement with the experiment can be achieved with the approaches of Green’s function and screened Coulomb interaction approximation. We demonstrate that our compounds have a direct band gap. The optical properties of MPbI3 are calculated using a density-functional perturbation theory. Our data shows that MPbI3 (M = Na, K) have a weak response to electromagnetic radiation at high photon energies and a strong response at low energies.

2016-06

International Journal of Astronomy (Issue : 2169) (Volume : 5)

Craters occur when an objects like Asteroids, Comets and Meteorites hits onto the surfaces of Moon and Planets and their impact has became a major geological process. The objective of the project is to investigate how the size of a Meteorite and Asteroid on the Moon and Planets is related to the size of impact crater. We started with a two round stone of different mass and size covered slightly with a layer of a viscous mud fluid as a fragmentation were dropped at variable height onto the flour. However, we have used a layer of sprinkles as a mineral diversity of the surface impacted. We have measured the diameter, depth and the Ejecta distance of the crater each time, there were three trails for each stone drop height. The results shows that, the crater diameter and the crater depth increased as the height and mass of the ball drop increased in addition of increasing Ejecta distance. .