Bond Angle Variations Research Articles

IMPACT OF Ca DOPING ON THE STRUCTURAL CHARACTERISTICS OF La1-XCaXFe0.5Mn0.5O3

A series of perovskite compounds La1-xCaxFe0.5Mn0.5O3 (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 and 0.9) were synthesized using the conventional ceramic method. The influence of the Ca-doping on the crystal structure of these compounds was studied using was investigated through X-ray diffraction (XRD) and Raman scattering spectroscopy. XRD analysis revealed that all the samples crystallize in an orthorhombic structure with the Pbnm space group. The variation in lattice parameters, bond lengths and bond angles created by the difference in valence state and ion size due to the Ca-doping leads to the distortion and tilt of octahedra in the samples.

Effect of Calcination Temperature on the Structural, Morphological, and Magnetic Properties of Rare-Earth Orthoferrite NdFeO3 Nanoparticles Synthesized by the Sol-Gel Method

The sol-gel technique has been used to synthesize rare Earth orthoferrite NdFeO3 nanopowders. The present investigation examines how calcination temperatures affect the structural, morphological, and magnetic properties of NdFeO3 orthoferrites. X-ray diffraction studies indicate that there is no discernible difference in the observed structures with calcination temperatures other than the bond distances and bond angles. The surface morphology and field-emission scanning electron microscopy (FESEM) indicate that porosity of the samples is regulated by the physical shape of the tiny particles within them. Porosity is minimized as calcination temperature increases, showing a higher density that contributes to reducing leakage current features while improving the break-down strength. These variations are attributed to bond length and bond angle variation of the Fe-O. The photocatalytic activity of the NdFeO3 nonoparticles was assessed by photodegrading a number of organic dyes, including methyl orange (MO), rhodamine B (RhB), and methylene blue (MB). The product displays significant photocatalytic degradation of the dyes whenever exposed to visible light. Overall, this investigation aims to establish a relationship between the physical properties and microstructural parameters to provide valuable insights into the magnetic interactions present in the samples and the comprehensive behavior of NdFeO3 orthoferrites samples calcination at different calcination temperatures.

AlN/GaN Superlattice band structure calculation Using Empirical Tight Binding Model

AlN/GaN superlattices are studied using the empirical tight-binding method (ETBM) with sp3 approximation. The model includes first-nearest-neighbor orbital interactions and accounts for the strain effect by modifying the ETBM parameters based on variations in bond lengths and angles. According to the authors knowledge, this study marks the first application of ETBM to determine the full band structure of AlN/GaN superlattices. On average, the ETBM band gaps resulting from this work are 7.48 % closer to the experimental data in comparison with Kronig-Penney outputs. In addition to the high accuracy of the model, the presented model is easier to implement compared to the density functional theory model.

Study on tensile properties of copper/graphene/2D-SiC composite materials: A molecular dynamics simulation

Van der Waals heterostructures composed of graphene and 2D-SiC generally exhibit outstanding electrical and mechanical properties. However, these structures are prone to brittle failure during damage, which greatly limits their application in practical engineering. Conversely, copper-based composite materials have been discovered to significantly enhance material toughness. Therefore, a novel copper/graphene/2D-SiC composite material is designed and molecular dynamics simulation is performed to investigate its mechanical properties under uniaxial tension. The results show that these composite materials possess the advantages of both high strength and toughness due to the heterostructure layer and the copper layer. Further analysis of the deformation mechanism of the copper layer indicates that it is mainly attributed to short-range atomic slip and the generation of Shockley partial dislocations. The heterostructure layer can partially impede the propagation of dislocations, enhancing the overall tensile strength of the composite materials. After the copper layer enters the plastic flow state, the variation of bond lengths and bond angles suggests that the heterostructure layer bears the tensile load, and the 2D-SiC layer is more prone to fracture due to higher stiffness compared to the graphene layer. Additionally, the influence of temperature and strain rate on the tensile properties is investigated. It is observed that increasing temperature could gradually reduce the tensile strength of the composite materials while the strain rate, within a certain range, has little effect.

Analyze the temperature-dependent elastic properties of single-walled boron nitride nanotubes by a modified energy method

The elastic properties of boron nitride nanotubes (BNNTs) were investigated utilizing an enhanced energy method. By considering small deformations and applying the principle of minimum potential energy, the variations in atomic bonds and bond angles within the nanotube structure were determined. The modified model incorporated the contribution of inversion energy to the overall potential energy of the system, leading to the derivation of analytical expressions for the Young's modulus, shear modulus, and strain energy of both armchair and zigzag BNNTs under varying temperatures. The results indicate that compared to zigzag BNNTs, the impact of inversion energy on the elastic constants of armchair BNNTs is more significant, especially at small diameters (<1 nm). In thermal environment, this study demonstrates that the change in Young's modulus of BNNTs is lower than that of carbon nanotubes (CNTs), confirming the superior thermal stability of BNNTs over CNTs. Furthermore, molecular structure mechanics (MSM) and continuum mechanics models were employed to analyze the strain energy of BNNTs. The effects of different bonds, bond angles, and inversion angles on strain energy were analyzed in a thermal environment, revealing distinct differences between the two types of BNNTs. These findings provide more accurate theoretical guidance for thermal applications based on the stretching of BNNTs.

Investigation on structural, electrical and magnetic properties of ErFeO3: Sintered at different temperature

This investigation reports the effect, on structural, electrical, and magnetic properties of ErFeO3 orthoferrites, sintered at different temperatures: 800 °C, 1000 °C, and 1200 °C. XRD analysis confirms that all the samples exhibit a single-phase orthorhombic structure. Raman studies indicate no significant variation in the observed Raman modes with increasing sintering temperature, suggesting that, the absence of crystal symmetry changes. Field-FESEM images reveal that the porosity of the samples is influenced by the shape of the grains present within them. Specifically, the sample sintered at 1000 °C exhibits higher porosity, resulting in higher leakage current density (J-E) compared to the other samples. The dielectric and magnetization parameters show an increase for the samples sintered at 1000 °C, while a decrease is observed for the samples sintered at 1200 °C. These variations are attributed to the bond length and bond angle variation of the Fe–O in the studied samples. Overall, this investigation aims, to establish a relationship between the physical properties and microstructural parameters, provide valuable insights into the magnetic interactions present in the samples and the comprehensive behavior of ErFeO3 orthoferrites samples sintered at different sintering temperatures will be discussed in this paper.

Exploring novel Cd(II) complexes with 5-methyl-4-imidazolecarboxaldehyde: synthesis, structure, computational insights, and affinity to DNA through switchSense methodology.

A series of four Cd(II) complexes with 5-methyl-4-imidazolecarboxaldehyde (L) with different inorganic anions within or outside the coordination sphere of general formula: [CdCl2L2] (1), [CdBr2L2] (2), [CdI2L2] (3), and [CdL4](PF6)2·3H2O (4) was synthesized through one-step and two-step reactions, respectively. All complexes were obtained as colorless crystals without the need for recrystallization and exhibited solubility in aqueous solutions. Structural analysis revealed different coordination environments for each complex, with variations in bond lengths and angles. The crystal packing of the complexes was stabilized by hydrogen bonding and π-π stacking interactions. FT-IR analysis indicated coordination of the ligand to the metal ion, and UV-Vis studies confirmed the stability of the complexes in solution. Computational analysis has revealed the polar nature of the complexes and their favorable stability constants. Affinity studies with DNA using the switchSense technique demonstrated rapid association and dissociation processes for all complexes, with temperature-dependent binding constants. Thermodynamic analysis suggested spontaneous with positive entropy change and endothermic formation processes for the complexes. Overall, the study underscores the synthesis, examination, and interaction with DNA of Cd(II) complexes, demonstrating their promise within medicinal chemistry.

Promoting structural distortion to enhance the crystal field strength of Mn(II) in tetrahedral bromide for near-unity yellow emission.

Two zero-dimensional hybrid manganese bromide polymorphs ((DMAPH)2MnBr4) exhibit single-crystal to single-crystal phase transformation, accompanied by an increase in MnBr4 tetrahedral bond angle variance (σ2). This structural change leads to an emission redshift due to enhanced crystal field strength, achieving yellow emission with near-unity quantum yield, which highlights its potential for solid-state lighting applications.

Phase-Dependence of Molecular Structures Arising from Weak London Dispersion Interactions.

ConspectusThe structures of molecules can be different in different phases. Intermolecular forces, even those of weak noncovalent interactions (WNCIs), can lead to a preference for quite different conformations in the solid, the gas, and the liquid phases. WNCIs can cause variations in bond lengths, angles, and torsional angles. Since structure is a fundamental concept in chemistry, the knowledge of structural changes with phase is important to understand the source and effects of distorting contributions from WNCIs but also as a predictive tool for the design and stabilization of new bonding situations.X-ray crystallography is ubiquitous and now mostly straightforward to perform, but facilities for the determination of accurate gas-phase structure determination are rare, and gas-phase work is laborious and time-consuming. There are currently about 1.25 million crystal structures and more than 12 500 experimental gas-phase structures, but the intersection of the two data sets that can tell us about the structural differences of the same molecule in different phases is surprisingly small.In this Account, we describe several cases of WNCI-dominated systems for which accurate experimental structure determinations exist for both the gas phase and the solid state and, in one case, also for solution. The examples include aryl-aryl, aryl-alkyl, and alkyl-alkyl interactions; systems with chalcogen and halogen bonding; and fluorine-based interactions in arylboranes. We work out the role of WNCIs in stabilizing large, strained, or sterically overloaded molecules. We will show how flexible molecules will fold under the action of WNCIs when isolated in the gas and how they fold or unfold when they are embedded in an environment of neighbors in crystals. We will show how they can vary in strength when the substitution patterns in aryl groups are changed by different halogens and how intramolecular WNCIs, such as those forming rings, change when such systems experience additional intermolecular WNCIs.Overall, we hope that this Account will give the reader an idea of the type and magnitude of structural changes that can be expected from a free molecule in the gas phase or a single molecule calculated by quantum chemistry compared with one embedded in a crystal. This should define the limits of comparability and provide some predictive concepts of the distortions and variations to be expected.

Eu3+ Site Distribution and Local Distortion of Photoluminescent Ca3 WO6 :(Eu3+ , K+ ) Double Perovskites as High-Color-Purity Red Phosphors.

In this study, Eu3+ and K+ co-doped Ca3 WO6 double perovskite, a high-color-purity red phosphor, is quantitatively investigated using synchrotron X-ray diffraction Rietveld refinement, energy dispersive X-ray spectroscopy, and high-resolution PL spectroscopy. The Eu3+ fluorescence line-narrowing (FLN) results, used to estimate the Eu3+ occupation at given sites (so-called A and B sites) in the host crystal (A2 BMO6 ; A, B=Ca; M=W), reveal that the Eu3+ ions have a twin distribution in both the A and B sites with high asymmetry ratios of ΛA =9.7 and ΛB =10.7, respectively. More interestingly, at lower Eu3+ doping levels, the ions are predominantly located at the B sites (≈75%), indicating that the high color purity of Ca3 WO6 :(Eu3+ , K+ ) is mainly caused by the high asymmetry ratios of the Eu3+ sites. Rietveld refinement combined with the FLN technique provides more reliable results for increasing the Eu3+ substitution at the A site with Eu3+ and K+ doping concentrations, which lower the lattice energy of Ca3 WO6 :(Eu3+ , K+ ). The structural distortions owing to K+ co-doping in terms of the quadratic elongation and bond-angle variance exhibit good correlations with the Ca(Eu)O12 A-site cuboctahedra and Ca(Eu)O6 B-site octahedra, partially accounting for the higher Λvalues.

A composite phase change material with large volume change rate for thermal underwater glider

The thermal underwater glider (TUG) is an important device currently used for exploring ocean resources and monitoring ocean temperature. The TUG harvests ocean thermal energy (OTE) through working medium and converts into net buoyancy variation for propulsion. The phase change material (PCM) filled in the thermal engine is the key working fluid for the TUG to harvest OTE. A large volume change rate of PCM at ocean temperature difference is important for improving the TUG's efficiency and performance. Previous studies focus on N-hexadecane for OTE conversion with limited performance. This paper proposes N-hexadecane (C16) based composite PCM for an improved thermal-to-mechanical conversion process. The experimental test results show that the composite PCM (C16:C24 = 9:1 wt%) exhibits a similar phase transition temperature (17.8–18.4℃) with C16 (18.2–18.6℃). As compared to pure C16, the volume shrinkage of this composite PCM was 26.67% higher than that of C16 and the volume expansion rate was 30.74% higher than that of C16, indicating that the composite PCM based TUG could output more net buoyancy variation and propulsion power. Following experimental test, molecular dynamics simulation of the composite PCM is carried out. The reason for this volume expansion/shrinkage improvement was revealed as the larger C–C bond length and H–C–C bond angle variations. The composite materials provided in this paper could potentially improve the propulsion performance of TUG.

Subpicosecond Molecular Rearrangements Affect Local Electric Fields and Auto-Dissociation in Water.

Molecular simulations of auto-dissociation of water molecules in an 81,000 atom bulk water system show that the electric field variations caused by local bond length and angle variations enhance proton transfer within ∼600 fs prior to auto-dissociation. In this paper, auto-dissociation relates to the initial separation of a proton from a water molecule to another, forming the H33O+ and OH- ions. Only transfers for which a proton's initial nearest covalently bonded oxygen remained the same for at least 1 ps prior to the transfer and for which that proton's new nearest acceptor oxygen remained the same for at least 1 ps after the transfer were evaluated. Electric fields from solvent atoms within 6 Å of a transferring proton (H*) are dominant, with little contribution from farther molecules. However, exclusion of the accepting oxygen in such electric field calculations shows that the field on H* from the other solvent atoms weakens as the time to transfer becomes less than 600 fs, indicating the primary importance of the accepting oxygen on enabling auto-dissociation. All resultant OH- and H3O+ ion pairs recombined at times greater than 1 ps after auto-dissociation. A concentration of 8.01 × 1017 cm-3 for these ion pairs was observed. The simulations indicate that transient auto-dissociation in water is more common than that inferred from dc-conductivity experiments (10-5 vs 10-7) and is consistent with the results of calculations that include nuclear quantum effects. The conductivity experiments require the rearrangement of farther water molecules to form hydrogen-bonded "water wires" that afford long-range and measurable proton transport away from the reaction site. Nonetheless, the relatively large number of picosecond-lived auto-dissociation products might be engineered within 2D layers and oriented external fields to offer new energy-related systems.

Investigate the effect of the synthesis method on the magnetic dynamic properties of SrAl4Fe8O19 hexaferrite

M-type SrAl4Fe8O19 hexaferrite was synthesized through three different synthesis methods, i.e., solid-state, co-precipitation, and sol–gel auto-combustion, to study the effect of synthesis on the structural and magnetic properties. X-ray diffraction (XRD), Rietveld refinement, high-resolution scanning electron microscope, and SQUID-magnetic property measurement system (MPMS) magnetometer were performed. The structural analysis demonstrated the formation of magnetoplumbite structure by these three synthesis methods. The variation in bond length and bond angle was also observed due to the synthesis methods, which affected the super-exchange interaction of the system. The solid-state method produced larger grains and more significant saturation magnetization i.e., 4.03 µm and 43.16 emu/gm, respectively, than the co-precipitate and sol–gel auto combustion methods. Magnetization–temperature (M−T) measurement revealed that the solid-state synthesized sample showed a higher blocking temperature than the rest. Magnetic susceptibility (χ) was performed with temperature dependence on different frequencies to demonstrate the magnetic dynamic properties of the SrAl4Fe8O19 hexaferrite. AC susceptibility results showed very strong magnetic interaction between particles leading to spin glass action at very low temperatures. The Neel–Arrhenius (N-A) & Vogel-Fulcher (V-F) models were used to determine the jump attempt time (τ0) and E0/KB (energy barrier or activation energy and Boltzmann constant) through AC susceptibility of magnetic particles. The τ0 and E0/KB were observed at about 2.84 × 10-11 sec and 871.31, respectively, for the solid-state synthesized sample by the V-F model.

Pressure and temperature effects on (TiZrTa)C medium-entropy carbide from first-principles

Multicomponent carbides have recently received considerable interest because of their remarkable material properties and vast material composition space compared to traditional carbides. However, the underlying physical mechanisms of multicomponent carbides remain poorly understood, particularly involving high pressure and temperature applications. Herein, the impacts of pressure and temperature on the stability, mechanical, and thermophysical properties of (TiZrTa)C are explored and evaluated by the density functional theory (DFT) computations. The study demonstrates that (TiZrTa)C is mechanically and thermally stable even at 100 GPa or 1500 K. (TiZrTa)C exhibits significant local lattice distortion, metallic conductivity, mechanical anisotropy, and covalent characteristics. Lattice distortion stems from the covalent bond length and angle variation caused by the random distribution of metal elements. Elevated pressure increases the elastic constants, Young's modulus, Bulk modulus, shear modulus, hardness, and fracture toughness of (TiZrTa)C. Increasing temperature leads to decrease the elastic constants and mechanical stiffness of (TiZrTa)C. The hybridization of C-p electrons and M-d electrons results in forming a pseudogap near the Fermi level and directional covalent bonds within the crystal. (TiZrTa)C has similar material properties to binary carbides, meaning that it has the potential to be used as a viable ultra-high temperature ceramic.

Magnetic studies of Mn2+substituted Zn-ferrite nanoparticles: Role of secondary phases, bond angles and magnetocrystalline anisotropy

Magnetic studies of MnxZn1–xFe2O4 (x = 0.5, 0.6, 0.7) nanoferrite particles prepared by sol-gel auto combustion method are presented. The deviation of the oxygen positional parameter (U) from the ideal value of 0.375 is an indicator for the cation redistribution in the present ferrite systems. The variation of bond angles estimated from the cation distribution seemed to be strengthening of A–B superexhange interaction. The nature of M − H loops revealed that the present ferrite nanoparticles are in the single domain state showing superparamagnetism. The saturation magnetization (Ms) increases while coercivity (Hc) decreases with the substitution of Mn2+ ion concentration. The highest value of Ms = 25 emu/g was reported for the composition x = 0.7. It was observed that the blocking temperature (TB) is decreasing and again increasing with the doping level of Mn2+. From FC-ZFC curves, the uneven variation of magnetization (M) at 10 K can be found. It attributes to the cation distribution in the ferrite samples at 10 K is different from those of at 300 K. The Mӧssbauer spectra revealed that the ferrite nanoparticles exhibited both quadruple and hyperfine interactions can be found in the composition x = 0.7 while the ferrite nanoparticles exhibited that only quadruple interaction can be in the compositions x = 0.5 and 0.6. The isomer shift (δ) values showed the presence of high spin Fe3+ ions only. The paramagnetic doublets having higher value of quadruple splitting (Δ) are assigned to the core structure while doublets lower value of quadruple splitting (Δ) is assigned to shell structure. The present results are incorporated in terms of cation distribution, magnetocrystalline anisotropy considering the core-shell morphology of ferrite nanoparticles.

Structural Behavior Of Garnet-Type Li7La3Zr2O12 Solid Electrolyte Material: A Classical Molecular Dynamics Study

The cubic garnet-type Li7La3Zr2O12 is an eminent candidate for next-generation solid state battery technology due to its thermal stability and high ionic conductivity. As such, its operation mechanisms need to be thoroughly understood, particularly focusing on the structural instability challenge reported to occur at lower temperatures. Herein, the statistical sampling capability of molecular dynamics simulations is employed during the investigation of fundamental structural, kinetic and thermodynamic properties emanating its subjection to pressure and temperature. Systematic induction of pressure yielded transition of the tetragonal phase to the cubic phase at 2 GPa pressure. The lattice parameters for the cubic and tetragonal phases, acquired in the current study are within 0.38 % agreement with literature. Furthermore, the XRD graphs confirm varying phases under different pressure conditions. The temperature phase diagram for 0 GPa structure agrees well with the literature trends and interestingly, the 2 GPa structure retained the cubic phase at various temperatures and confirmed in the XRDs and temperature phase diagram. Interrogatio of LaO8 dodecahedral and ZrO6 octahedra demonstrated no significant variations in bond lengths and bond angles giving a good indication for the regulation of Li+-transport channel size in the 2 GPa structure. Efforts in this study are a preliminary stage to fully understanding the thermodynamic impact as a structural modification avenue pending further investigations.

Transforming incipient to real ferroelectrics in SrTiO3 upon doping luminescent Eu3+ /Tb3+ ions and the generation of white light for piezo-phototronics application

A novel effort has been given to transform the incipient ferroelectrics behavior to real in SrTiO3 and to generate white-light emission by doping luminescent Eu3+ and Tb3+ ions. Ferroelectric study showed that upon doping Eu3+ ion, SrTiO3 became pure ferroelectric in nature and upon co-doping Tb3+ ion there is a significant enhancement of the saturation polarization. Photoluminescence study showed that both the Eu3+ doped and Eu3+& Tb3+ co-doped compounds are white-light-emitting materials due to perfect combination of blue light originated from defect centers present in the host with the green and red emissions from the dopant ions. Such white-light-emitting materials with controlled piezo potential may not need external excitation energy and have potential application in many flexible optoelectronic devices. Lifetime study confirmed the existence of two components for both the dopant ions and suggested that there is an asymmetric environment created due to distortion of geometry, which is linked to ferroelectric property. Finally, all the experimental results were supported by Hybrid functional based theoretical calculation. We have observed that the bond angle variance (BAV) parameter and distortion index (DI), which are directly linked with the distortion in the matrix, are responsible for ferroelectric behavior and they follow the order with the dopant ions as Eu3+&Tb3+>Tb3+>Eu3+. This corroborates well with the experimentally observed trend of the saturation polarization.

Uniaxially Strained Graphene: Structural Characteristics and G-Mode Splitting.

The potential use of graphene in various strain engineering applications requires an accurate characterization of its properties when the material is under different mechanical loads. In this work, we present the strain dependence of the geometrical characteristics at the atomic level and the Raman active G-band evolution in a uniaxially strained graphene monolayer, using density functional theory methods as well as molecular dynamics atomistic simulations for strains that extend up to the structural failure. The bond length and bond angle variations with strain, applied either along the zigzag or along the armchair direction, are discussed and analytical relations describing this dependence are provided. The G-mode splitting with strain, as obtained by first principles’ methods, is also presented. While for small strains, up to around 1%, the G-band splitting is symmetrical in the two perpendicular directions of tension considered here, this is no longer the case for larger values of strains where the splitting appears to be larger for strains along the zigzag direction. Further, a crossing is observed between the lower frequency split G-mode component and the out-of-plane optical mode at the Γ point for large uniaxial strains (>20%) along the zigzag direction.

RETRACTED: Influence of Different Rotations of Organic Formamidinium Molecule on Electronic and Optical Properties of FAPbBr3 Perovskite

Hybrid organic–inorganic halide perovskites (HOIPs) have recently represented a material breakthrough for optoelectronic applications. Obviously, studying the interactions between the central organic cation and the Pb-X inorganic octahedral could provide a better understanding of HOIPs. In this work, we used a first-principles theoretical study to investigate the effect of different orientations of central formamidinium cation (FA+) on the electronic and optical properties of FAPbBr3 hybrid perovskite. In order to do this, the band structure (with and without spin–orbit coupling (SOC)), density of states (DOS), partial density of states (PDOS), electron density, distortion index, bond angle variance, dielectric function, and absorption spectra were computed. The findings revealed that a change in the orientation of FA+ caused some disorders in the distribution of interactions, resulting in the formation of some specific energy levels in the structure. The interactions between the inorganic and organic parts in different directions create a distortion index in the bonds of the inorganic octahedral, thus leading to a change in the volume of PbBr6. This is the main reason for the variations observed in the electronic and optical properties of FAPbBr3. The obtained results can be helpful in solar-cell applications.

RETRACTED: The Effect of Structural Phase Transitions on Electronic and Optical Properties of CsPbI3 Pure Inorganic Perovskites

Hybrid inorganic perovskites (HIPs) have been developed in recent years as new high-efficiency semiconductors with a wide range of uses in various optoelectronic applications such as solar cells and light-emitting diodes (LEDs). In this work, we used a first-principles theoretical study to investigate the effects of phase transition on the electronic and optical properties of CsPbI3 pure inorganic perovskites. The results showed that at temperatures over 300 °C, the structure of CsPbI3 exhibits a cube phase (pm3m) with no tilt of PbI6 octahedra (distortion index = 0 and bond angle variance = 0). As the temperature decreases (approximately to room temperature), the PbI6 octahedra is tilted, and the distortion index and bond angle variance increase. Around room temperature, the CsPbI3 structure enters an orthorhombic phase with two tilts PbI6 octahedra. It was found that changing the halogens in all structures reduces the volume of PbI6 octahedra. The tilted PbI6 octahedra causes the distribution of interactions to vary drastically, which leads to a change in band gap energy. This is the main reason for the red and blue shifts in the absorption spectrum of CsPbI3. In general, it can be said that the origin of all changes in the structural, electronic, and optical properties of HIPs is the changes in the volume, orientation, and distortion index of PbI6 octahedra.