Dielectric Refractive Index Research Articles

Analysis of Enhanced Optical and Electronic Properties of Bismuthene with Pd, Pt Adsorption for Advanced Optoelectronics

This study examines the nanostructures formed after the adsorption of palladium (Pd) and platinum (Pt) metals over bismuthene monolayer. It is emphasized that the adsorption of Pd and Pt significantly influences the optical absorption characteristics of bismuthene. The computational simulations based on density functional theory investigate how adding Pd and Pt metals to bismuthene changes its electronic and optical properties. Pure bismuthene displays substantial optical absorption, primarily in the visible region. When Pd and Pt atoms adsorb over the surface of bismuthene, the absorption coefficient value in the visible and near‐infrared region is enhanced with redshift. Adsorption of Pd and Pt also leads to significant changes in the dielectric constant and refractive index of bismuthene, with distinct peaks observed in the dielectric constant at lower energy after adsorption. Nanostructures composed of Pd/bismuthene and Pt/bismuthene have the potential to predict stable configurations, which makes them appropriate for the absorption of light in the visible and near‐infrared regions. Because of the stable and improved optical absorption accomplished in the desired range of the electromagnetic spectrum, these nanostructures can be utilized for a variety of applications, including but not limited to solar cells and photodetectors, as well as photovoltaics and IR sensor applications.

First-principles investigation of structural, electronic, and optical properties of RVO4 (R = Er, Eu, Tb, Yb) orthovanadates under pressure

Abstract First-principles calculations were performed to systematically study RVO4 orthovanadates with tetragonal zircon- and scheelite-type structures. The study focused on structural parameters, pressure-induced structural phase transformation, electronic band structure, and optical properties under ambient conditions and hydrostatic pressures up to 10 GPa. Energy-volume and enthalpy-pressure curves were used to determine the phase transition pressures of RVO4 compounds. Among the four compounds examined in both phases, YbVO4 was determined to be less compressible than the other compounds. The computed band structures indicated that RVO4 compounds in both phases are semiconductors with a direct bandgap at the Γ→ Γ point. Optical spectra such as dielectric constants, refractive index, reflectivity, absorption coefficient, birefringence, optical conductivity, and energy loss function were computed as functions of incident radiation energy in the energy range of 0–45 eV. The optical anisotropy of RVO4 compounds was observed in both phases. The computed birefringence values for zircon (scheelite) RVO4 indicate that they are uniaxial positive (negative) crystals and have a large birefringence value. Hydrostatic pressure was found to play an important role in the structural, optical, and electronic properties of both phases of RVO4 compounds.

Influence of Alkyl Chain Length and Bromine Substitution on Thermal, Photophysical, and Optical Properties of Biphenyl Luminescent Molecules

This study investigates a series of bromine-substituted alkoxy biphenyl derivatives to explore their potential as luminescent and optical materials for applications in display technologies, sensors, and photonic devices. Four compounds were synthesized, including 5-Br, 6-Br, 7-Br, and a comparative non-halogenated molecule 6-H. The findings reveal that the bromine-substituted derivatives exhibit enhanced thermal stability as the alkoxy chain length increases, though none of the compounds displayed liquid crystalline phases, likely due to molecular flexibility and steric hindrance from the bromine atoms. Photophysical studies showed that the compounds exhibit tunable emission colors ranging from green to blue, depending on the side chain length and the presence or absence of bromine. Importantly, the introduction of bromine was found to enhance the photophysical properties, including increased quantum yields and longer emission lifetimes, compared to the non-halogenated analog. Moreover, these luminescent molecules can maintain strong fluorescence both in solution and when forming aggregates. Furthermore, the optical properties, such as dielectric constant, extinction coefficient, refractive index, and optical conductivity, were thoroughly examined. The results indicate that structural variations, including alkyl chain length and bromine substitution, significantly influence the capability of these materials to store and dissipate electrical energy. Their strong optical responses, high energy storage capabilities, and sensitivity to structural modifications suggest that the studied materials have substantial potential for applications in energy storage, sensing, optoelectronics, and non-linear optics. These findings offer important guidelines for the rational design of multifunctional luminescent and optical materials, representing a significant step forward in the development of practical applications of smart materials and advanced photonic devices.

Investigating the differences in the optical properties and laser photoluminescence for chitosan films extracted from two different origins

This work carefully examines the variations in chitosan films derived from shrimp and crab shells in terms of their optical characteristics and laser-induced photoluminescence. Chitosan was dissolved in acetic acid and then cast into films to create chitosan films. The functional properties of chitosan generated from crab and prawns were shown to differ in specific spectrum regions due to differences in hydrogen bonding, degree of deacetylation, and structural conformations, as indicated by the FTIR study. Using TD-DFT and TD-DFT/CASTEP simulations, computational studies were carried out to predict the chitosan samples' molecular structures and frequency characteristics. Measurements and analyses were done on the optical characteristics, such as absorbance, refractive index, dielectric constants, and optical conductivity. Chitosan from shrimp shells (chitosan 2) and crab shells (chitosan 1) differed significantly in terms of UV absorbance, refractive index, dielectric constant, and optical conductivity, according to the study. Chitosan 2 showed increased dielectric constant, refractive index, and UV absorbance, indicating higher optical conductivity and a larger capacity for electrical energy storage, making it a better fit for optoelectronic applications. Chitosan's optical and photoluminescence characteristics are greatly influenced by its place of origin. These results emphasize how crucial it is to choose the right source material for a given optical application, especially in domains, where precise control over UV absorption and refractive index is necessary.

Optical properties of polyvinyl alcohol-glass waste powder composites

This study investigates the effect of glass waste powder content on the UV–Vis spectroscopy of polyvinyl alcohol (PVA). The glass powder was obtained from the waste of fluorescent tubes. The solution casting method was utilized to prepare PVA- glass composite films by adding glass powder with 10, 20, 30, and 40 wt. %. UV–Vis absorption spectra of PVA- glass samples were recorded in the range 220–1100 nm. The optical parameters were calculated as follow: absorbance, absorption coefficient, transmittance, refractive index, extinction coefficient, dielectric constant, and imaginary dielectric constant. Based on the XRD results, it is revealed that the PVA become more amorphous with increasing amount of glass waste. UV–Vis spectroscopy studies demonstrated that, for all samples, the absorbance, absorption coefficient, extinction coefficient, and Ei increases with the increase in the amount of glass waste. On the other hand, transmittance decreases with increasing amount of glass waste. The change of the studied properties with wavelength depends strongly on the amount of glass waste powder. At visible region, the transmittance is stable with increasing wavelength for samples containing 20, 30 and 40%. Glass waste, while the pure sample and the sample containing 10% glass waste, the transmittance increases with the wavelength. On the other hand, the absorbance and absorption coefficient for all samples decreases rapidly up to a specific wavelength and then the change is very slight at longer wavelengths. Also, the increase of extinction coefficient and imaginary dielectric constant with wavelength is related to the amount of glass powder added. The change of dielectric constant and refractive index with wavelength depends on the amount of the filler, where the pure and the sample filled with 10% glass powder show normal dispersion, while the other samples show anomalous dispersion. Finally, the pure sample had the highest energy gap (5.7 eV) while the sample containing 30% glass powder had the lowest value (4.8 eV). Through this study, it become possible to change the optical properties of PVA by adding glass waste powder, which allows the possibility of benefiting from the new composites to be used in different applications according to their response to different wavelengths. From an economic and environmental point of view, these wastes can be utilized instead of being thrown away by reusing them as polymer fillers, taking into consideration the change in the optical properties of the matrix polymer.

DFT Analysis of Structural, Electrical, and Optical Properties of S, Si, and F-Doped GeO2 Rutile

This study examines the structural, electrical, and optical properties of S-, Si-, and F-doped GeO2 rutile with a 6.25% doping concentration using density functional theory (DFT) and the FP-LAPW method. The results show that the structural parameters align with previous studies. Doping reduces the band gap from 4.09 eV for pure GeO2 to 1.98 eV for GeO1.9375Si0.0625. The optical properties, including dielectric constant, conductivity, refractive index, and absorption spectrum, were analyzed up to 13 eV, revealing anisotropy along the zz (001) and xx (100) axes. These doped materials are promising for UV-sensitive photonic detectors, as they remain efficient even under sunlight exposure in the visible and infrared spectra. This could lead to the development of photodetection devices suitable for bright environments where traditional detectors are affected by sunlight.

Structural, electronic, mechanical, optical and magnetic properties of RhNbZ (Z = Li, Si, As) Half-Heusler compounds: a first-principles study

Abstract Structural, mechanical, electronic, optical and magnetic properties of the cubic RhNbZ (Z = Li, Si, As) half-Heusler compounds is reported using density functional theory (DFT) as implemented in quantum espresso simulation package. Structurally, the compounds are most stable when they are in type I atomic arrangement. Studies of mechanical properties indicate that all the three compounds are ductile in nature and mechanically stable. Calculations of electronic band structure and density of states (DOS) affirm that RhNbSi is a semi-conductor with an indirect band gap of 0.662 eV and 1.0095 eV from generalized gradient approximation (GGA) and GGA+U approaches respectively, where U is Hubbard parameter, RhNbLi has metallic property under both GGA and GGA+U approaches whereas RhNbAs has metallic nature under GGA prediction but it has half-metallic property under GGA+U approach, a property which is essential for spintronic applications. Optical parameters such as dielectric function, reflectivity, refractive index, extinction coefficient, absorption coefficient, optical conductivity and electron energy loss were estimated in the photon energy range of 0–40 eV. Results from these properties calculations reveal that both absorption coefficient and optical conductivity have maximum values whereas electron energy loss has minimum value in the lower energy ranges which show that the materials under our study can be considered as potential candidates for optoelectronic applications. From magnetic property calculations, RhNbSi is predicted to be nonmagnetic material but RhNbLi and RhNbAs have magnetic nature.

First-Principles insights into ferromagnetic, optoelectronic and dynamical properties of Eu/Er Co-doped AlGaN

Abstract In this thorough investigation, we analyze the complex electronic, magnetic, and structural properties of wurtzite-structured aluminum gallium nitride (Al0.125Ga0.75N) when co-doped with the rare-earth elements erbium and europium. Leveraging a modified LSDA+U approach that adeptly captures the pivotal interactions within the 4f shell, our findings unveil that the co-doped AlGaN exhibits distinct semiconducting behavior. Remarkably, in stark contrast to its pristine Al0.125Ga0.75N counterpart, the co-doped material manifests an indirect band gap whose value is notably reduced. This intriguing phenomenon of ferromagnetism observed in the co-doped system can be attributed to the intricate interplay between the f-p and p-d states, culminating in the formation of hybridized f-p-d orbitals. Our investigation further elucidates the intricate hybridization of various orbitals at the valence band maximum (VBM), including the harmonious fusion of p-d orbitals derived from Eu-5d, Er-5d, and N-2p. Notably, the magnetic moment exhibits a pronounced localization at the Eu and Er sites, attaining substantial values of 5.90 μB and 2.99 μB, respectively. Moreover, our comprehensive exploration encompasses the calculation of the real and imaginary components of the dielectric function, refractive index, and extinction coefficient, spanning an impressive photon energy range of up to 12 eV. Significantly, in the ultraviolet region of the optical spectrum, the imaginary part of the Eu and Er co-doped Al0.125Ga0.75N unveils a pronounced absorption coefficient, a pivotal property with far-reaching implications for optoelectronic applications.


Strain effect on structural, electronic and optical properties of Gra/MoS2 heterobilayer

Abstract Heterobilayers formed by stacking graphene and MoS2 monolayers have been successfully synthesized in the laboratory, presenting a highly promising material with versatile applications due to its flexibility and enhanced optical properties. In this study, we employ density functional theory to investigate the impact of biaxial and uniaxial strain on the structural, electronic and optical properties of Graphene/MoS2 (Gra/MoS2) heterobilayer. The unstrained Gra/MoS2 is shown to be a thermodynamically stable structure with binding energy − 0.736 eV and a band gap of 1.899 meV, which opens at the Dirac point of graphene. Gra/MoS2 is also shown to have a better refractive index and absorption coefficient when compared to MoS2 monolayer in the visible region. Under biaxial strain, heterobilayer became unstable as the structure of both monolayers changed. The variation of biaxial strain from −4% to 4% enables tuning of the band gap within a range of 1.07–6.623 meV. The Fermi level shifted towards the conduction band under compressive strain and towards the valence band under expansive strain. Manipulation of biaxial strain also facilitates tunability in energy peaks for optical properties such as the real and imaginary parts of the dielectric function, refractive index and absorption coefficient in the visible spectrum. In contrast, uniaxial strain induces minimal changes in the overall structure and stability of the heterobilayer, resulting in a limited band gap range of 1.118–2.4 meV. Furthermore, uniaxial strain fails to introduce significant tunability in the optical properties of the heterobilayer.

Computational investigation of the phase stability, electronic, optical, phonon spectrum, and elastic behavior of layered perovskites Ca2XO4 (X = Zr, Hf) for optoelectronic applications.

A significant class of solid-state materials, Ruddlesden-Popper (RP) perovskites are well-known for their rich chemical compositions that make them excellent electrocatalysts. Therefore, in this work, we conduct thorough analysis of RP perovskites, specifically Ca2XO4 (X = Zr, Hf). We delve into the structural, electronic, optical, and mechanical properties presenting their insights for the first time. Our investigations reveal that Ca2XO4 (X = Zr, Hf) exhibits stable tetragonal phase structures, with energies (E0) of - 10,522.93eV and - 33,520.14eV, respectively. The calculated in terms of the ground state determines to possess distinct values such as - 4.79 eV/atom for LiScTe2 and - 3.95 eV/atom for Ca2ZrO4 and Ca2HfO4. Notably, the semiconductor characteristics of Ca2ZrO4 and Ca2HfO4 are underscored by their respective wide direct band gap of 5.02eV and 5.30eV. Then, we discuss the optical parameters encompassing the dielectric function, absorption coefficient, optical conductivity, refractive index, and energy loss function. is described as ductile, whereas is defined as brittle. Our outcomes underscore remarkable ability of these materials to absorb ultraviolet radiation from the electromagnetic spectrum, positioning them as promising candidates for optoelectronic applications. We made these calculations by employing first-principles approach rooted in density functional theory (DFT) and utilizing the Perdew-Burke-Ernzerhof-Generalized Gradient Approximation (PBE-GGA) and Tran and Blaha-modified Becke-Johnson (TB-mBJ) functional within the WEIN2K framework. In this framework, Kramers-Kronig relations are used to obtain crucial optical parameters. Mechanical behavior is assessed by employing Voigt-Reuss-Hill approximation (VRH) fulfilling the Born's criteria which emphasizes that these materials are equally appropriate for a broad range of mechanical applications.

Deep learning of spectra: Predicting the dielectric function of semiconductors

Predicting spectra and related properties such as the dielectric function of crystalline materials based on machine learning has a huge, hitherto unexplored, technological potential. For this reason, we create an database of 9915 dielectric tensors of semiconductors and insulators calculated in the independent-particle approximation (IPA). In addition, we present the family of machine learning models, a series of graph attention neural networks (GAT) trained to predict the dielectric function and refractive index. yields accurate prediction of spectra of semiconductors using only their crystal structure. Smooth, artifact-free curves are obtained without these properties being enforced by penalties. Published by the American Physical Society 2024

Mechanical, electronic, optical, and thermoelectric properties of Rb2TlGaX6 (X = F, I) lead-free double perovskites: a first-principles study

Abstract Halide perovskites play an important role in the renewable energy industry and are the top substitutes for Pb-halide perovskites. This study investigates the structural, mechanical, electronic, optical, and thermoelectric properties of the double halide perovskites Rb2TlGaX6 (X = F, I) using density functional theory (DFT) at WIEN2k interfaces. The structural, mechanical, and thermal stabilities are evaluated using the tolerance factor, Born-Huang criteria, and negative formation energy. The obtained lattice constants are 9.31 Å and 24.93 Å, for Rb2TlGaF6 and Rb2TlGaI6 respectively. Rb2TlGaF6 is brittle and Rb2TlGaI6 is ductile. Both compounds exhibit anisotropic behavior. The indirect semiconducting nature (L-X) is demonstrated by the estimated bandgap values of 6.05 eV (4.31 eV) and 1.06 eV (0.52 eV), for Rb2TlGaF6 and Rb2TlGaI6 respectively, using the TB-mBJ (PBE-GGA) potential. Distinctive optical characteristics are studied, including the dielectric function, loss function, conductivity, reflectivity, refractive index, and absorption coefficient. Based on the investigation, both materials exhibit excellent optical conductivity, high light absorption throughout the UV–visible spectrum, and low reflection (within 20% for Rb2TlGaF6 and 40% for Rb2TlGaI6). Lastly, various thermoelectric properties are explored by varying the temperature. Both compounds show a high Seebeck coefficient and low thermal conductivity. The maximum figure of merit (ZT) obtains of 0.61 and 0.81, for Rb2TlGaF6 and Rb2TlGaI6, respectively. These results demonstrate the suitability of Rb2TlGaF6 and Rb2TlGaI6 for thermoelectric and photovoltaic applications.

Exploring photocatalytic and photovoltaic applications of chalcogenide Perovskites, ABS3 (A = Li, Na, K, Rb, Cs; B = Si, Ge, Sn): A First-Principles investigation using the HSE-06 hybrid functional

Unlike traditional semiconductors, chalcogenide perovskites offer a unique combination, merging the stability and safety of oxides with the tunability of halide semiconductors, making them particularly promising for photocatalytic and photovoltaic applications. This paper theoretically investigates the optoelectronic properties of the triclinic ABS3 (A = Li, Na, K, Rb, Cs; B = Si, Ge, Sn) perovskites using density functional theory with the HSE06 hybrid functional. The feasibility of synthesizing ABS3 materials was revealed using formation energy calculations. Band structure and density of state calculations confirm that all compounds under investigation are semiconductors exhibiting indirect bandgaps. These bandgaps increase with the ionic radius of the A-site cation, following the trend Li < Na < K < Rb < Cs. Additionally, the order of bandgap energies for the B-site elements is observed as Si > Sn > Ge. This trend emphasizes the significant influence of cation size on the electronic properties of perovskite materials. The investigated perovskites exhibit bandgaps between 1.67 and 3.55 eV, with a narrow difference (0.03–0.49 eV) between their indirect and direct gaps. We additionally compute various optical parameters (dielectric function, refractive index, extinction coefficient, optical conductivity, absorption coefficient, reflectivity, and energy loss function) across the 0–50 eV energy range. The valence and conduction band edge potentials of ABS3 perovskites were calculated to evaluate their potential applications in water splitting, carbon dioxide reduction, and photodegradation processes. The results of this study demonstrate that several ABS3 semiconductors exhibit promising characteristics that position them as efficient photocatalysts for these photocatalytic reactions. LiGeS3 and NaGeS3, in particular, are promising for solar cell applications.

Investigations of optoelectronic, magnetic, and transport properties of Zintl-phosphides BaX2P2 (X=Cd, Sn, Cu) for green technology: First principle calculations

One way to decarbonize the world's energy generation is through thin-film photovoltaics (PV), there are significant problems with elemental abundance, stability, or performance with the thin-film solar absorbers that are now on the market. We present the optoelectronic and transport properties of Zintl-phosphides BaX2P2 (X = Cd, Sn, Cu) using first-principles calculations based on density functional theory. Our calculations show that increasing the band gap of Cd/Sn and Cu-based phosphides from 0.5 to 4.0 eV enables fine adjustment of bandgaps, structure, and optoelectronics, broadening the material's potential applications in the semiconducting industry. Strong absorption occurs in the energy range of 4–8 eV; it concluded that their optical characteristics, such as natural and imaginary dielectric functions, refractive index, and absorption coefficient, might make them useful in optoelectronic and photovoltaic applications. In the 50–800 K temperature range, power factor (PF), electrical conductivity, thermal conductivity, and Seebeck coefficient were investigated. With PFs of approximately 7.5 × 1010 W/K2ms, respectively, the compound demonstrated a considerable potential utility in thermoelectric devices. An assessment of radiation shielding performance was conducted using the XCOM tool across a broad energy range ranging from 15 keV to 15 MeV. The findings indicated that the mass attenuation coefficient (GMAC) values increased proportionately of BaCd2P2, BaSn2P2, and BaCu2P2 samples. The GMAC peaked for all sample compositions at around 0.015 MeV, with values spanning from 42.94 cm2/g for BaCd2P2 to 51.96 cm2/g for BaCu2P2. Nevertheless, when elevating the energy level beyond 15 keV, a notable decline in GMAC values was observed. This is likely mostly attributable to the predominance of photoelectric interactions at lower energy levels. These compounds' strong absorption patterns and high PF make them promising materials for thermoelectric and photovoltaic applications.

Investigating the physical properties of the binary compound CdTe under different pressures using FP-LMTO method

The structural, electronic and optical properties of Cadmium Telluride (CdTe) are investigated at different pressures using the full potential linear muffin-tin orbital FP-LMTO method based on density functional theory (DFT), within the local density approximation LDA and the generalized gradient approximation GGA approximations were used to calculate the exchange-correlation potential. The ground state properties of CdTe compound were determined for diverse phases, and the band structure and optical parameters were calculated at pressures ranging from 0 GPa to 50 GPa. Optical parameters, including real part, imaginary part of the dielectric function, reflectivity, refractive index, extinction coefficient and energy loss function, were calculated for over an energy range from 0 eV to 13.6058 eV. The results were compared with available experimental and theoretical data, showing good agreement with earlier reported result. These particularities reveal that CdTe as favorable material for optoelectronic applications, as it exhibits together important electronic and optical responses under different pressure.

Low-Cost Optical Filters Based on SiOxCy:H and Ag Thin Films Fabricated by Plasma Enhanced Chemical Vapor Deposition and Sputtering

Hexamethyldisiloxane (HMDSO) is an organosilicon compound with a modifiable bandgap, depending on the deposition conditions. This material has many unique properties due to its stability, low toxicity, and strong adhesion, making it useful as a protective barrier against corrosion, moisture, and oxidation. In this work, HMDSO films were deposited on glass substrates by the Plasma Enhanced Chemical Vapor Deposition (PECVD) technique at different deposition times. The optical properties of HMDSO films, such as dielectric permittivity, refractive index, extinction and absorption coefficients, and band gap energy, are inferred from transmission and reflection spectra. As the deposition time increased, the real part of the dielectric constant, the refractive index, and the bandgap energy showed a decrease, dropping from 4.24 to 3.40, from 2.06 to 1.84, and from 2.85 eV to 2.03 eV, respectively. The latter result is determined using classical models such as the O’Leary-Johnson-Lim (‘OJL’) interband transition and the harmonic oscillator model. HMDSO and Silver are used in this study for the fabrication of optical filters using two types of structures, a multiple cavity metal–dielectric (MCMD) and the Fabry–Perot structure. The silver layers are deposited by a sputtering process. The MCMD optical filter shows a higher transmittance of about 30%, but a wide range of wavelengths is transmitted. In contrast, the Fabry–Perot filter showed high contrast but a lower transmittance of about 20%.

High thermal energy storage of the two-dimensional Al2Te3 semiconductor: DFT study of stability, electronic, phonon, thermal, and optical properties based on GGA and HSE06

The present study investigates the structural, electronic, thermal, and optical properties of a novel two-dimensional Al2Te3 using GGA and HSE06 functional in the framework of density functional theory. The formation energy, the phonon dispersion, and AIMD calculations confirm the structural, dynamical, and thermal stability of Al2Te3, respectively. The electronic band structure and partial density of states indicate the semiconducting characteristics of 2D Al2Te3 with band gap values of 1.92 eV (GGA) and 2.78 eV (HSE06). The thermal properties of Al2Te3 reveal a high heat capacity due to a very high phonon density of states. This property signifies the material's growing ability to store thermal energy. Thus the entropy demonstrates a continuous increase with temperature, adhering to the second law of thermodynamics. The analysis of optical properties of Al2Te3 demonstrates strong light interaction in the ultraviolet, UV, region, and the optical band gap is found to be larger than the electronic band gap for both GGA and HSE06 functional due to indirect behavior of the band gap. Furthermore, the static dielectric function, refractive index, and optical conductivity are found to be smaller in the case of HSE06 compared to the GGA which may be due to reduced transition probability, and less screening effects including in the HSE06 functional. These findings offer valuable insights into the potential applications of Al2Te3 in various fields, including thermal energy storage and optoelectronics.

Investigations of optoelectronic and scintillating properties of novel halide perovskites Cs2KSnX6 (X=Cl, Br, I)

In this paper, using density functional theory (DFT) formalism, optoelectronic properties of new halide perovskites Cs2KSnX6 (X = Cl, Br, I) are explored. The lattice constants of these double perovskites with Cl,Br, and I were found to be 11.75Å,12.34Å, and 13.24Å, respectively. Trans-Blaha modified Becke-Johnson (TB-mBJ) exchange-correlation functional was used to calculate the energy bandgap by incorporating spin-orbital coupling effects into it. The double perovskite with Cl was observed to possess a higher band gap value due to the increase in the size of halide anions. Due to the inverse relationship between bandgap values and lattice constants, it has been observed that increasing the lattice constant value results in the decrease of the electronic band gap and vice versa. From the density of states calculations, the nature of the electronic states involved in forming the energy bands has been determined. The upper light yield (LY) with the limit of 100 % under ideal conditions is found to be 544217 ph/MeV, 950118 ph/MeV, and 1600000 ph/MeV for Cs2KSnCl6,Cs2KSnBr6, and Cs2KSnI6 respectively, which suggests their potential applications in scintillating devices. Moreover, the optical properties like complex dielectric functions, absorption coefficients, reflectivity, and refractive index are calculated for these new proposed compounds. A systematic analysis of the optical and scintillating properties suggests the usefulness of Cs2KSnI6 among other compounds, as a potential candidate for high-energy radiation detection and other optoelectronic applications.

Theoretical investigation of transition metal (Cr, Fe)-Doped AlN in a rocksalt structure: A DFT study on physical properties

This study presents first-principles computations to explore the structural, electronic, optical, elastic, vibrational, and thermodynamic properties of Aluminum Nitride (AlN) doped with the transition metals Chromium (Cr) and Iron (Fe) in the rocksalt structure. Using spin-polarized density functional theory (DFT) within the CASTEP code, we applied GGA-PBE, GGA + U, and HSE06 approximations for exchange-correlation functions. Our results reveal that Cr doping transforms AlN into a dilute magnetic semiconductor (DMS), while Fe doping induces a transition to a metallic state. Both Al0.₇₅Cr₀.₂₅N and Al₀.₇₅Fe₀.₂₅N exhibit strong covalent bonding, contributing to enhanced hardness. The substantial increase in static dielectric constant and refractive index suggests strong optical responses. Furthermore, our analysis confirms the mechanical and dynamic stability of these compounds. Al₀.₇₅Cr₀.₂₅N is a promising candidate for electronic and spintronic applications, whereas Al₀.₇₅Fe₀.₂₅N, with its high conductivity, is well-suited for magnetic storage devices and electrical contacts. Our findings for AlN are consistent with prior theoretical and experimental data, while the results for Al₀.₇₅Cr₀.₂₅N and Al₀.₇₅Fe₀.₂₅N offer novel insights for future research.

Study on the optical properties of Sm3+ doped bismuth silicate crystals based on first principles

Abstract This study systematically investigated the effect of Sm3+ doping on the optical properties of bismuth silicate (Bi4Si3O12, abbreviated as BSO) crystals using first principles calculations based on density functional theory (DFT). By calculating the dielectric function, reflectivity, absorption coefficient, refractive index, conductivity, and energy loss function of BSO crystals under different Sm3+ doping ratios, we found that moderate Sm3+ doping can increase the dielectric function of BSO crystals, and the real part of the dielectric function represents the material’s ability to respond to the electric field, that is, the macroscopic polarization degree. Therefore, moderate Sm3+ doping enhances the polarization ability of BSO crystals. Simultaneously doping an appropriate amount can effectively enhance the conductivity and light (visible and infrared) absorption ability of BSO crystals, and reduce the energy loss between electrons in BSO crystals, thereby improving their luminescence performance. Specifically, when the Sm3+ doping ratio is 1/6, the optical properties of BSO crystals are significantly improved. These findings not only enhance the understanding of the mechanism of optical performance changes in rare earth ion doped BSO crystals, but also provide a theoretical basis for the development of new rare earth doped optical materials.