Lead-free cubic CsXF3 (X = Sn, Ge, Zn, Sr) fluoride perovskites are promising, environmentally friendly candidates for sustainable optoelectronic technologies. In this work, their structural, energetic, lattice dynamical, and broadband optical properties are systematically investigated using density functional theory (DFT). Comparative functional assessments demonstrate that the generalized gradient approximation of Perdew–Burke–Ernzerhof (GGA-PBE) method provides superior structural accuracy over PBE revised for solids (PBEsol) and successfully curbs the artificial atomic over-binding inherent to local density approximation (LDA). Total energy and Goldschmidt tolerance factor analyses confirm robust thermodynamic stability against decomposition. However, harmonic phonon dispersion calculations reveal critical dynamical instabilities within the ideal cubic lattice at 0 K for CsSnF3, CsGeF3, and CsSrF3 due to pronounced imaginary modes, whereas CsZnF3 exhibits near-complete dynamic stability. Beyond structural profiles, this research emphasizes how diverse electronic configurations customize each compound for targeted device architectures. Specifically, the direct bandgaps of CsSnF3 (1.74 eV) and CsGeF3 (2.04 eV), combined with high optical conductivity, position them as exceptional visible-light harvesting photovoltaic absorbers. Conversely, the wide transparency windows and localized wide-bandgap profiles of CsZnF3 (3.64 eV) and CsSrF3 (6.29 eV) optimize them for solar-blind photodetectors and deep-ultraviolet (UV) optical windows, respectively. Crucially, planar average charge density and electrostatic potential analyses reveal that lone-pair-driven strong internal electric fields tailor CsSnF3 and CsGeF3 for active ferroelectric applications, whereas the uniform ionic charge distribution of CsZnF3 and CsSrF3 favors their utilization as reliable gate insulators and energy storage capacitors. Finally, spin–orbit coupling (SOC) assessments confirm that relativistic effects are negligible. Ultimately, these theoretical insights establish critical microscopic design guidelines for fluoroperovskite-based energy technologies.
The morphological, structural, and optical characterization of the SnS thin film deposited by the ultrasonic spray pyrolysis (USP) method was carried out. Simple and inexpensive commercial ultrasonic nano-mist device was used to deposit SnS thin film. The solution procedure was developed to obtain highly oriented SnS thin film. The SnS thin film exhibited an orthorhombic crystal structure with a strong (111) preferred orientation. The crystallite size was calculated as 56 nm. A direct band gap of 1.21 eV was determined from the Tauc plot. Raman spectroscopy was performed to identify the phases present in the films. The FTO/TiO2/SnS/Au solar cells were fabricated. The ideality factor and saturation current of the device were calculated as 3.02 and 2.59 × 10−6 A, respectively. The series resistance of 370 Ω was obtained using Cheung’s method. The photovoltaic parameters of the champion cell with a power conversion efficiency (PCE) of 0.388% were found to be Jsc = 6.50 mA/cm2, Voc = 0.207 V, and FF = 28.9%. In addition, the photodiode performance of the cell was evaluated.
The structural, electronic, vibrational, optical, and thermodynamic properties of yttrium hydrogen chalcogenides (YHS, YHSe, and YHTe) are systematically investigated using first-principles density functional theory (DFT), with phonon and thermodynamic properties determined using Phonopy calculations. All compounds are dynamically stable, exhibiting progressive lattice expansion from YHS to YHTe due to increasing chalcogen atomic size. Additionally chalcogen substitution effectively tunes the electronic structure by modulating the band gap and density of states (DOS) through enhanced hybridization between Y-d and chalcogen-p orbitals. Spin–orbit coupling (SOC) introduces subtle yet non-negligible modifications, with stronger effects observed for heavier chalcogens Te-based systems. The band gaps show slight SOC-induced variations, changing from 1.6385 to 1.6472 eV for YHS, 1.5152 to 1.5172 eV for YHSe, and from 1.52 to 1.42 eV for YHTe, reflecting enhanced relativistic effects in Te-based systems. YHS and YHSe retain indirect band gaps semiconductor, whereas YHTe exhibits a robust direct band gap semiconductor. Phonon dispersion confirms dynamical stability and reveals systematic softening of vibrational modes from YHS to YHTe, attributed to increased atomic mass and reduced interatomic force constants. This behavior correlates with enhanced electronic polarizability and modified bonding. Optical properties exhibit a red shift in the absorption edge with increased dielectric response. Thermodynamic analysis shows that entropy and specific heat increase with temperature, while Helmholtz free energy decreases and becomes more negative from YHS to YHTe, indicating improved thermodynamic stability. These findings highlight yttrium hydrogen chalcogenide compounds as promising tunable materials for optoelectronic and energy applications.
The objective of this study is to investigate the structural and electrical characteristics of the superconducting compound Y1 − xInxBa2Cu3O7 + δ (x = 0, 0.1, 0.2, 0.3, and 0.4), synthesized via the standard solid-state reaction method. The critical transition temperature and energy gap were determined using the four-point probe technique, while the structural parameters were quantitatively analyzed using Scherrer, Williamson–Hall (W–H), and size–strain plot (SSP) methods. All substituted samples exhibited metallic behavior in the normal state prior to transitioning to the superconducting state. Notably, the x = 0.3 sample demonstrated an enhanced critical temperature (Tc(offset) = 104.8 K) and a corresponding energy gap of ~0.032 eV. Structural characterization revealed that this concentration yields a minimized crystallite size of 6.118 nm accompanied by a specific induced lattice microstrain of 0.0019. The substitution of Y+3 by isovalent In+3 alters the lattice parameters, which may optimize the physical configuration between the charge reservoir layers and the superconducting CuO2 planes. This study establishes that controlled lattice microstrain induced by appropriate indium substitution plays a critical role in optimizing charge-transfer efficiency and enhancing high-temperature superconductivity within the Y-123 system.
First-principles density functional theory (DFT) calculations were performed to examine the structural, electronic, optical, and mechanical properties of tetragonal InCuX2 compounds (X = S, Se, Te). The results of the band structure and density of states (DOS) calculations confirm metallic behavior for InCuS2, InCuSe2, and InCuTe2, characterized by a zero band gap, indicating their potential for high conductivity applications. Mulliken population and Hirshfeld charge analyses reveal significant Cu-X covalency and charge delocalization, supporting the metallic nature of these compounds. Bond population analysis further shows that shorter Cu-S bonds (2.33 & Aring;) enhance the structural stability and stiffness of InCuS2, while larger chalcogen atomic radii in InCuSe2 and InCuTe2 weaken In-X interactions, improving flexibility. The optical analysis highlights high dielectric constants (epsilon ' approximate to 30 for InCuSe2) and substantial optical absorption (alpha approximate to 2.5 & times; 105 cm-1 for InCuS2), suggesting their suitability for optoelectronic and photonic applications. Elastic property evaluations show that InCuS2 possesses the highest stiffness (C11 = 235.3 GPa, E = 80.3 GPa), whereas InCuTe2 exhibits increased ductility (E = 11.8 GPa). These results demonstrate the tunable metallicity, electrical conductivity, optical response, and mechanical resilience of InCuX2 materials, positioning them as promising candidates for next-generation electronic, thermoelectric, and optoelectronic devices.
The study of one-dimensional (1D) multiferroic spin chain systems exhibiting magnetoelectric coupling continues to be a primary emphasis in condensed matter physics. The interplay between magnetic and elastic degrees of freedom, the so-called magnon-phonon coupling, plays an important role in magnetism, with the ability to transport quantum information over long distances. Using the Green's function technique, we investigate the phonon dynamics for a 1D frustrated Heisenberg antiferromagnetic (AFM) spin-1 where the cycloidal spin state is the ground state in the highly frustrated parameter region. Following the Holstein-Primakoff transformation in the context of the modified spin-wave approximation (MSWA), the phonon's relaxation function provides a measure of the acoustic phonon energy and the linewidth. We show that the inclusion of the Dzyaloshinskii-Moriya (DM) interaction consolidates the spin states by attenuating the phonon's relaxation factor (acoustic phonon energy) and enhances magnetic effects (magnon energy) and the linewidth, both essential to exotic quantum transport phenomena like topological magnonic effects, spintronic technology, quantum information storage, spin-caloritronics, et cetera.
We highlight a theoretical investigation of the structure, electronic states, and optical response of the polar intermetallic complex CsLa in this article. The proposed hexagonal noncentrosymmetric structure has been optimized using density functional theory (DFT) in the framework of GGA and Perdew-Burke-Ernzerhof (PBE), demonstrating a small expansion and a comparatively low bulk modulus-features that represent mechanical softness. Density of states (DOS) and band structure calculations clearly establish metallic conductivity, dominated by La-5d and Cs-5p orbital contributions at the Fermi level. Significant anisotropy is revealed by optical analysis: reflectance, absorption spectra, and dielectric constants are all significantly changed with crystallographic orientations. Additionally, efficient charge transport and directional energy dissipation properties can be achieved by high static dielectric values and clear, relatively small energy absorption peaks. These characteristics suggest that CsLa might be applicable in energy conversion devices, high-k dielectric applications, and infrared photonics. Overall, CsLa emerges as a promising candidate for multifunctional optoelectronic materials due to its symmetry-breaking geometry combined with metallic conductivity and anisotropic optical response.
In this study, DFT approach is used by applying Kohn-Sham/Hartree-Fock-coupled perturbation method within generalized gradient approximation (GGA)-Perdew Burke Ernzerhof (PBE) and GGA + U functional to estimate structural, optical, electronic, mechanical, and thermodynamic properties of oxy-sulfates family (XCuSO, X = La, Lu, Sc, and Y) compounds. Electronic properties reveal strong influence of metallic cations on the band gap values (1.17 to 1.63 eV), which have presented semiconductor natures. Optical properties such as dielectric function values (8-12) and strong optical absorption (> 10(5) cm(-1)) have been calculated along with strong refractive index, extinction coefficient, optical conductivity, which are appeared in the visible region of spectra, showing the potential of compounds for energy conversion applications. Mechanical properties have been explored to estimate the ductile-brittle natures of the compounds, and have resulted with ductile natures for YCuSO and LuCuSO and brittle for LaCuSO and ScCuSO compounds. Moreover, thermodynamics characteristics have been examined up to 1000 K temperature range indicating potential of the compounds to be used for application up to 600 K (operating window). All such outcomes are presenting the potential of compounds for energy conversion applications such as photovoltaics (PVs).
Density functional theory (DFT) calculations within the local density approximation (LDA) method were employed to investigate the electronic structure and tuning mechanisms of framework-substituted Type-I tin-based clathrates. The calculation reveals that Ga (or Al) preferentially occupies Wyckoff 6c crystallographic sites, whereas the remaining framework-substituted atoms reside at 16i sites, significantly enhancing the material stability. For K8Ga8Sn38, we investigated two configurations involving a Ga-Ga-bond-free structure (i) and a Ga-Ga-bond-maximized variant (ii). Configuration (ii) is energetically disfavored because of the asymmetric bond strength distribution within the Ga-centered tetrahedral sp(3) network. The structural effects of guest and framework substitution in the Rb8Al8Sn38 clathrate were studied. K2Rb6Al8Sn38, formed by substituting K for Rb in dodecahedra, increased the bulk modulus B-0 to 46.092 GPa versus 43.369 GPa for Rb8Al8Sn38, indicating enhanced cage-guest size matching and rigidity. Concurrent Al-Sn bond strength recovery offset volume expansion. Conversely, Ga substitution yielding Rb8Ga8Sn38 decreased B-0 to 40.955 GPa, revealing poorer size matching and increased strain at larger volumes. The nonmonotonic B-0 vs. volume behavior stems from dual effects, including framework bond strength and guest-cage size matching. All the compounds are semiconductors, with intrinsic bandgaps decreasing as follows: 0.6247 eV (Rb8Ga8Sn38) > 0.6019 eV (Rb8Al8Sn38) > 0.5932 eV (K2Rb6Al8Sn38). This reduction is attributed to Al-p orbital contributions lowering the conduction band minimum (CBM) and a sharp decrease in the K-atom density of states (DOS) near the conduction band edge.
The study focuses on analyzing the physical, structural, and optical characteristics of ACdF3 (A = Cu, Li, and Fr) metal halide perovskites. The computed lattice constants exhibit converging results with the values of the existing literature, which exhibits the precision and dependability of the information gathered from this study. The mechanical properties of the compounds CuCdF3 and FrCdF3 exhibit ductility, whereas LiCdF3 exhibits brittleness in nature. These compounds show anisotropic behavior in each direction, and the inter-atomic binding bonds show the predominantly ionic characteristics of these materials. The band gap of CuCdF3 shows a notable reduction and exhibits characteristics resembling ultra-narrow band-gap semiconductor behavior with a band gap value of 0.027 and 0.016 eV for GGA-PBE and Hybrid HSe06 functional. The band gap of LiCdF3 demonstrates semiconductor-like behavior with a value of 2.62 and 3.066 eV, whereas FrCdF3 shows an insulator nature with wide band gaps of 3.144 and 3.816 eV. Optical properties are studied for applications in coating materials, photodetectors, and optoelectronic devices due to their band gap, higher absorption, lower reflectivity, and lower loss function. Weak electronic spin orientation of the compounds demonstrates dielectric behavior. Furthermore, the poor reflectivity of CuCdF3 crystal makes the compound a potential candidate for anti-reflective coatings, electrode materials, and other optoelectronic devices in conducting industries.
This study employs first-principles density functional theory (DFT) within the GGA + U framework to systematically investigate the structural, electronic, and optical properties of Eu3+-doped ZnO at concentrations of 3.13%, 4.17%, and 6.25%. The calculated lattice parameters and band gap of pristine ZnO are consistent with previously reported theoretical and experimental results, confirming the reliability of the adopted computational methodology. Substitutional Eu incorporation leads to concentration-dependent lattice expansion and induces noticeable modifications in the electronic structure, while preserving the direct band-gap nature of ZnO. The band gap shows a slight but systematic modulation with increasing Eu content, associated with Eu-4f-related impurity states near the band edges. Optical analysis reveals modified dielectric behavior, reduced ultraviolet (UV) absorption intensity, and enhanced absorption in the visible region, accompanied by a blue shift of the dominant UV absorption edge. These results demonstrate that Eu doping enables effective tuning of ZnO’s electronic and optical response, highlighting its potential for UV-responsive optoelectronic applications such as UV photodetectors and transparent functional coatings.
In this study, we investigate the structural, electronic, and elastic properties of the lead-free halide perovskite CsSnCl3 using first-principles calculations based on density functional theory (DFT). The frequency-dependent optical properties were evaluated through the complex dielectric function computed within time-dependent density functional theory using the Sternheimer equation approach. The structural analysis reveals a stable cubic crystal structure with a lattice constant of 5.63 & Aring;. The electronic band structure, calculated using the generalized gradient approximation (GGA) with the Perdew-Burke-Ernzerhof (PBE) functional, shows a direct band gap of 1.06 eV, indicating promising semiconducting behavior suitable for optoelectronic applications. The elastic constants were also evaluated to understand the mechanical behavior of the compound. Key elastic parameters at zero pressure include a bulk modulus of 22.653 GPa, Pugh's ratio of 2.299, and Poisson's ratio of 0.305. These values confirm that CsSnCl3 is mechanically stable and ductile. The combination of a suitable band gap and favorable mechanical characteristics positions CsSnCl3 as a viable, environmentally friendly alternative to lead-based perovskites for use in light-harvesting devices. This article provides fundamental insights that support the potential applications of CsSnCl3 in photovoltaic and optoelectronic technologies, while also contributing to the ongoing development of sustainable materials for next-generation energy solutions.
Phase change materials (PCMs) are an important group of materials with distinct solid phases. In this group, Ge 2 Sb 2 Te 5 (GST) is a promising compound with many technological applications. GST can be grown into a heterostructure where the phase change is spatially confined, resulting in improved efficiency. In the present work, the electronic properties and electrical conductivity of GST heterostructures with various stacking configurations are studied using density functional calculations. Geometry optimization calculations show the importance of the van der Waals (vdW) correction that results in a decrease of the out‐of‐plane lattice parameter. Band structure calculations show metallic or semimetallic character for some configurations, whereas the others are semiconductors with bandgaps below 1 eV near the Γ point. The in‐plane electrical conductivity is higher than the out‐of‐plane one, with differences between the configurations at most three‐ to fourfold, indicating they all belong to the same phase. The Te atoms are negatively charged, while the Ge and Sb atoms have positive charges. There is no significant charge transfer between the blocks separated by vdW gaps although visible electron accumulation occurs within the gaps. The observed stacking‐dependent changes can possibly be applied to the design of interfacial PCMs with new properties and functionalities.
We present an extensive quantum Monte Carlo (QMC) study of a nearest‐neighbor, singlet‐projection model on the pyrochlore lattice that exhibits SO( N ) symmetry and is sign‐problem‐free. We found that, in contrast to the previously studied two‐dimensional (2D) variations of this model that harbor critical points between their ground state phases, the non‐bipartite pyrochlore lattice in three spatial dimensions appears to exhibit a first‐order transition between a magnetically‐ordered (MO) phase and some, as yet uncharacterized, paramagnetic (PM) phase. We also observe that the MO phase survives to a relatively large value of N = 8 and that it is gone for N = 9.
We calculate the Rashba coefficient and Rashba spin splitting for the first subband of the Al 0.6 Ga 0.4 N/GaN/Al 0.6 Ga 0.4 N quantum well (QW) with an inserted Al x Ga 1 − x N layer. The inserted Al x Ga 1 − x N layer enhances the inherent structure inversion asymmetry (SIA), increases the effective thickness of the GaN triangular potential well, as well as significantly changes the polarization electric field and the electron probability density. Due to the probability density and electric field around the left well (GaN layer) being rather high, contributions to the Rashba coefficient from the left well and the left interface are dominant. These contributions also increase with the Al concentration ( x ) in the inserted Al x Ga 1 − x N layer. The increasing polarization electric field, combined with the movement of electrons toward the left interface, collectively leads to an increase in both the Rashba coefficient and Rashba spin splitting at the Fermi level as a function of x . Our findings indicate that adding an Al x Ga 1 − x N layer can significantly enhance the Rashba coefficient and Rashba spin splitting in AlGaN/GaN QWs, providing valuable insights for the design of spintronic devices. PACS number(s): 71.70.-d , 73.21.-b , 78.30.Fs
