2025-02

Plos One

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.

2025-01

Semiconductor Physics, Quantum Electronics & Optoelectronics (القضية : 4) (الحجم : 27)

Abstract. 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.

2023-07

UKRAINIAN JOURNAL OF PHYSICAL OPTICS (القضية : 3) (الحجم : 24)

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.