Band Structure Calculations Research Articles

Surface terminations control charge transfer from bulk to surface states in topological insulators

Topological insulators (TI) hold significant potential for various electronic and optoelectronic devices that rely on the Dirac surface state (DSS), including spintronic and thermoelectric devices, as well as terahertz detectors. The behavior of electrons within the DSS plays a pivotal role in the performance of such devices. It is expected that DSS appear on a surface of three dimensional(3D) TI by mechanical exfoliation. However, it is not always the case that the surface terminating atomic configuration and corresponding band structures are homogeneous. In order to investigate the impact of surface terminating atomic configurations on electron dynamics, we meticulously examined the electron dynamics at the exfoliated surface of a crystalline 3D TI (Bi2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document}Se3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_3$$\\end{document}) with time, space, and energy resolutions. Based on our comprehensive band structure calculations, we found that on one of the Se-terminated surfaces, DSS is located within the bulk band gap, with no other surface states manifesting within this region. On this particular surface, photoexcited electrons within the conduction band effectively relax towards DSS and tend to linger at the Dirac point for extended periods of time. It is worth emphasizing that these distinct characteristics of DSS are exclusively observed on this particular surface.

First principle study of X2GaAgCl6 (X = Cs, Rb) double perovskites: structural, mechanical, vibrational, electronic, optical, SLME, thermoelectric, and thermodynamic properties for solar cell applications.

The structural, mechanical, vibrational, electronic, optical, SLME, thermoelectric, and thermodynamic properties of X2GaAgCl6 (X = Cs, Rb), a double perovskite material, were computed by employing Density Functional Theory (DFT). CASTEP and Quantum ESPRESSO were used to perform first-principles calculations. X2GaAgCl6 possesses a cubic structure with the space-group symmetry Fm-3m. The lattice parameters of Cs2GaAgCl6 and Rb2GaAgCl6 were optimized using the energy-volume curves, resulting in values of 7.357Å and 7.365Å, respectively. The population analysis confirmed the charge transfer among transition metals and halogen atoms. The stability of crystal X2GaAgCl6 (X = Cs, Rb) is effectively demonstrated by analyzing phonon dispersion curves with no negative frequencies. The band structure calculations indicated the semiconducting nature of compounds with energy gaps of 0.96eV and 0.88eV for Cs2GaAgCl6 and Rb2GaAgCl6, respectively. The optical characteristics results confirm that the examined materials are suitable for devices working, primarily in the electromagnetic spectrum's visible region. SLME results showed that Cs2GaAgCl6 has 30% and Rb2GaAgCl6 has 27% efficiency, respectively, suggesting their use in photovoltaics. The thermoelectric properties of X2GaAgCl6 (X = Cs, Rb) were calculated by using the BoltzTraP code in the temperature range of 300 to 800K. The quasi-harmonic Debye model was applied to calculate the thermodynamic characteristics.

Element-specific Curie temperatures and Heisenberg criticality in ferrimagnetic Gd6(Mn1−xFex)23 via Kouvel-Fisher analysis

Many large unit-cell rare-earth transition metal ternary alloys of the type Ra(M1−xM’x)b exhibit non-monotonic ferrimagnetic Curie temperatures (TC) coupled to monotonic composition-controlled magnetization. Its origin remains an important long-standing puzzle in the absence of studies probing their temperature-dependent element-specific magnetism. Here, in order to resolve this issue and identify design principles for new R-M-M’ permanent magnets, we carry out x-ray magnetic circular dichroism (XMCD) for the series Gd6(Mn1−xFex)23, x = 0.0 − 0.75. The results show that the net Mn-moment reduces and switches from parallel to antiparallel for x ≥ 0.2, while the Fe-moment is always antiparallel to the Gd-moment. Kouvel-Fisher analyses of XMCD data reveals distinct sublattice TC’s and 3D Heisenberg criticality. Band structure calculations show magnetic moments and density of states consistent with experiments. The magnetic phase diagram shows three regions characterized by (i) Mn-sublattice bulk-TC > Gd-sublattice TC, (ii) a reduced common-TC for all sublattices, and (iii) Fe-sublattice bulk-TC > Gd-sublattice TC. The Mn-moment switching and gradual increase of Fe-moment combine to cause non-monotonic TC’s with monotonic magnetization. The study indicates the importance of element-specific TC’s for tuning magnetic properties.

Significant improvement in structural, electronic, optical and thermoelectric properties of PdTe2 in bulk and monolayer phase: A G0W0+BSE approach

Using first principles calculations structural, electronic, thermoelectric and optical properties of PdTe2 in bulk and monolayer were investigated. The calculated lattice parameters with different exchange correlation functionals show that the results obtained with addition of van der Waals corrections (vdW-DFC09x) are very well matched with the results obtained experimental. For correct prediction of electronic band gap, G0W0 approximation is used and the calculated band structure reveal that PdTe2 in bulk form has metallic nature as attained in experimental studies. In addition, the electronic band gap results with G0W0 approximation depicted that PdTe2 in monolayer phase is a semiconductor material with a direct band gap of 1.12 eV. The optical spectra have been calculated via many-body perturbation theory (MBPT) by solving Bethe-Salpeter equation (BSE) (G0W0+BSE). Ultimately, the results of optical spectra demonstrated that PdTe2 in monolayer phase has strong optical absorption within visible light wavelengths than the bulk phase which is good for solar cell applications. Thermoelectric (TE) properties of PdTe2 in bulk and monolayer structures have been studied using BoltzTraP code. The TE properties calculations indicated that better performance can be obtained by reducing the dimensionality of materials. The figure of merit was found to be above unity for monolayer phase. This paper successfully exploited the enhancement of the figure of merit values with the monolayer structure of PdTe2 material.

Two-dimensional monolayer BiSnO3: a novel wide-band-gap semiconductor with high stability and strong ultraviolet absorption

The exploration of two-dimensional (2D) wide-band-gap semiconductors (WBGSs) holds significant scientific and technological importance in the field of condensed matter physics and is actively being pursued in optoelectronic research. In this study, we present the discovery of a novel WBGS, namely monolayer BiSnO3, using first-principles calculations in conjunction with the quasi-particle G0W0 approximation. Our calculations confirm that monolayer BiSnO3 exhibits moderate cleavage energy, positive phonon modes, mechanical resilience, and high temperature resistance (up to 1000 K), which demonstrate its structural stability, flexibility, and potential for experimental realization. Furthermore, band-structure calculations reveal that monolayer BiSnO3 is a typical WBGS material with a band-gap energy (E g) of 3.61 eV and possesses a unique quasi-direct electronic feature due to its quasi-flat valence band. The highest occupied valence flat-band originates from the electronic hybridization between Bi-6p and O-2p states, which are in close proximity to the Fermi level. Remarkably, monolayer BiSnO3 exhibits a high absorption capacity for ultraviolet light spanning the UVA to UVC regions, displaying optical isotropy absorption and an unusual excitonic effect. These intriguing structural and electronic properties establish monolayer BiSnO3 as a promising candidate for the development of new multi-function-integrated electronic and optoelectronic devices in the emerging field of 2D WBGSs.

First-principles study on stability and superconductivity of ternary hydride LaYHx (x = 2, 3, 6 and 8)

Abstract Recent studies have shown that the La- and Y-hydrides can exhibit significant superconducting properties under high pressures. In this paper, we investigate the stability, electronic and superconducting properties of LaYH x (x = 2, 3, 6 and 8) under 0–200 GPa. It is found that LaYH2 stabilizes in the C2/m phase at ambient pressure, and transforms to the Pmmn phase at 67 GPa. LaYH3 stabilizes in the C2/m phase at ambient pressure, and undergoes phase transitions of C2/m → P21/m → R3m at 12 GPa and 87 GPa, respectively. LaYH6 stabilizes in the P43212 phase at ambient pressure, and undergoes phase transitions of P43212 → P4/mmm → Cmcm at 28 GPa and 79 GPa, respectively. LaYH8 stabilizes in the Imma phase at 60 GPa and transforms to the P4/mmm phase at 117 GPa. Calculations of the electronic band structures show that the P4/mmm-LaYH8 and all phases of LaYH2 and LaYH3 exhibit metallic character. For the metallic phases, we then study their superconducting properties. The calculated superconducting transition temperatures (T c) are 0.47 K for C2/m-LaYH2 at 0 GPa, 0 K for C2/m-LaYH3 at 0 GPa, and 55.51 K for P4/mmm-LaYH8 at 50 GPa.

Meta-GGA study of 2D AlN/BN planer heterostructure and performance enhancement via strain engineering.

The 2D AlN/BN planer heterostructure is a promising wide band gap semiconductor, but systematic studies of its bandgap and optical characteristics under applied strain are scarce. Here, the engineering property of 2D AlN/BN comprising bandgap nature transition and optical absorption capability (from unstrained to strained) have been investigated using density functional theory calculations. The formation energy calculations confirm the stability of the simulated nanoheterostructure. The electronic band structure calculations demonstrate that nanoheterostructure is an indirect bandgap material with a large bandgap of 5.26 eV, which can be modified effectively by applying strain. According to the calculations, the transition from indirect to direct band gap behavior has been observed at +15% biaxial strain with 2.71 eV band gap energy. Meanwhile, calculations for optical absorption and dielectric function reveal that the system has significant absorption peaks in the ultraviolet region which are very sensitive to applied strain. As strain increases, the first absorption peaks are shifted towards a lower energy range from 5.73 eV (Ꜫ= 0 %) to 3.76 eV (Ꜫ = +15%), which features an enhancement of optical absorption for solar and solar-blind regions. Furthermore, we determined that the band edge positions in 2D AlN/BN straddled the water redox potential under strain, indicating its effectiveness as a proficient photocatalyst. These characteristics make 2D AlN/BN planer nanoheterostructure a promising candidate for applications in optoelectronics and photocatalytic water splitting performance. First principles computations based on density functional theory were employed to carry out all the calculations with a self-consistent approach. For solving the Kohn-Sham equations, the first principles dependent full-potential linearized augmented plane wave scheme were adopted. For addressing the exchange-correlation effects, the generalized gradient approximation of PBEsol functional was used. To prevent interaction between the periodic images, we have inserted a vacuum region of 10 Å in the z-direction. Non-negligible weak dispersion corrections in nanoheterostructure were considered by using the DFT-D3 method of Grimme's. The locally modified Becke-Johnson (lmBJ) exchange potential has also been applied to compute electronic and optical properties in this research to obtain more accurate information.

Investigation of structural, electrical, magnetic, and optical properties of Cu (111) and the impact of Ag adatoms adsorption: A density functional theory study

Our study conducts a comprehensive investigation on the structural, electrical, magnetic and optical properties of pure Cu with a (111) crystallographic orientation, as well as the impact of the adsorption of Ag adatoms on a Cu (111) surface. To perform this analysis, we utilized the full potential linearized augmented plane-wave (FP-LAPW) approach in conjunction with Generalized Gradient Approximations (GGA + U) and the Wien2k simulation software. Specifically, we calculated electrical and optical properties including the band structure, density of states (DOS) for the Cu (111) surface with and without the presence of adsorbed Ag atoms. Based on the observed results, the overlapping of the electronic bands for simple Cu (111) is comparatively less than that of adsorbed Ag/Cu (111) slab, indicating higher conductivity. Moreover, the evolutions are also observed which are mainly due to d orbitals of Cu and Ag for Cu (111) and Cu/Ag (111) respectively. The calculated magnetic optimization and weak diamagnetic magnetic moments shows weak diamagnetism in these materials. The optical properties like Dielectric Function(ε), Refractive index(n), Extinction co-efficient(k), Reflectivity(R), Energy Loss (L), Absorption (α) and Optical conduction (σ) are calculated. Our research examines the importance of band structure calculation in relation to optical properties. We discuss how plasmon-energy plays a crucial role in producing peaks in the energy loss function, with a crystallographic axis of 13.7 eV and 13.6 eV for both Cu (111) and Ag/Cu (111) slab. In addition, we calculated the static dielectric function, absorption coefficient, and refraction values for these materials. Reflectivity spectra for both Cu (111) and Ag/Cu (111) exhibits Infra-red region, indicating good coating materials to reduce heating, for the application of electrical appliances and for optical application like anti-reflecting coating, optical fibers and solar cells.

The effects of V doping on the intrinsic properties of SmFe10Co2 alloys: A theoretical investigation

The present study focuses on the intrinsic properties of the SmFe10Co2-xVx (x = 0–2) alloys, which includes the SmFe10Co2 alloy, one of the most promising permanent magnets with the ThMn12 type of structure due to its large saturation magnetization (µ0Ms = 1.78 T), high Curie temperature (Tc = 859 K), and anisotropy field (µ0Ha = 12 T) experimentally obtained. Unfortunately, its low coercivity (<0.4 T) hinders its use in permanent magnet applications. The effect of V-doping on magnetization, magnetocrystalline anisotropy energy, and Curie temperature is investigated by electronic band structure calculations. The spin-polarized fully relativistic Korringa-Kohn-Rostoker (SPR-KKR) band structure method, which employs the coherent potential approximation (CPA) to deal with substitutional disorder, has been used. The Hubbard-U correction to local spin density approximation (LSDA + U) was used to account for the large correlation effects due to the 4f electronic states of Sm. The computed magnetic moments and magnetocrystalline anisotropy energies were compared with existing experimental data to validate the theoretical approach’s reliability. The exchange-coupling parameters from the Heisenberg model were used for obtaining the mean-field estimated Curie temperature. The magnetic anisotropy energy was separated into contributions from transition metals and Sm, and its relationships with the local environment, interatomic distances, and valence electron delocalization were analyzed. The suitability of the hypothetical SmFe10CoV alloy for permanent magnet manufacture was assessed using the calculated anisotropy field, magnetic hardness, and intrinsic magnetic properties.

Exploring the structural, mechanical, magneto-electronic and thermophysical properties of f electron based XNpO3 perovskites (X = Na, Cs, Ca, Ra).

Here, we present systematic investigation of the structural and mechanical stability, electronic profile and thermophysical properties of f-electron based XNPO3 (X = Na, Cs, Ca, Ra) perovskites by first principles calculations. The structural optimization, tolerance factor criteria depicts the cubic structural stability of these alloys. Further, the stability of these materials is also determined by the cohesive and formation energy calculations along with mechanical stability criteria. The electronic structure is explored by calculating band structure and density of states which reveal the well-known half-metallic nature of the materials. Further, we have calculated different thermodynamic parameters including specific heat capacity, thermal expansion, Gruneisen parameter and their variation with temperature and pressure. The thermoelectric effectiveness of these materials is predicted in terms of Seebeck coefficient, electrical conductivity and power factor. All-inclusive we can say that calculated properties of these half-metallic materials extend their route in spintronics, thermoelectric and radioisotope generators device applications.

Structural, elastic, mechanical, electronic, and optical properties of cubic K2Pb2O3 from first-principle study.

Based on first principles, the structure, elasticity, mechanics, electronics, and optical properties of cubic K2Pb2O3 were studied. The structural parameters calculated by this method are close to the previous theoretical results. The elastic constant, bulk modulus, shear modulus, Young's modulus, Poisson's ratio, and mechanical stability are studied, and it is shown that cubic K2Pb2O3 is mechanically stable, isotropic, and brittleness. The electrical conductivity and chemical bonding of cubic K2Pb2O3 were analyzed based on the calculated band structure, density of states (DOS), and bond populations. The dispersion of optical functions, including the dielectric function, refractive index, extinction coefficient, reflectivity, absorption coefficient, and loss function, is displayed and analyzed. All computations have been carried out based on density functional theory (DFT) as implemented in the CASTEP code. The norm conservation pseudopotential method is used to exchange correlation functionals within the generalized gradient approximation (GGA).

Effects of Mo doping on the structure, adsorption performance, and photocatalytic activity of LaFeO3 nanoparticles: Experimental and DFT studies

In this study, a series of Mo-doped LaFeO3 composite photocatalyst nanoparticles (x-LFMO, x = 0.33, 0.5, 0.67) were synthesized by ultrasonic-assisted sol–gel method under controlled Mo doping. X-ray diffraction (XRD) analyses indicate that Mo substitutes one-third of the Fe atoms in the B site of the LaFeO3 to form orthogonal perovskite structures LaFe0.67Mo0.33O3, which is the only pure phase crystal formed at stoichiometric Fe to Mo ratios of 2:1, 1:1, and 1:2, respectively. SEM and N2 adsorption/desorption revealed significantly smaller particle sizes (30–50 nm) and the formation of rich channels after Mo doping, thus enriching the specific surface area and pore size dispersion. DRS confirmed that the Mo-doped LFO composites exhibit significantly enhanced absorption in the visible region. This can be further explained by DFT theoretical calculations of energy band structures and density of states, which demonstrate that the effective mass of the electrons in LaFe0.67Mo0.33O3 is reduced and the off-domain properties of the electrons are enhanced, facilitating the excitation and transport of the photogenerated electrons. Kinetic studies showed that Mo-doped composite nanoparticles exhibit excellent adsorption capacity for quinoline, indole, and pyridine, and the pure phase LaFe0.67Mo0.33O3 and 0.5-LFMO performed well for them with removal efficiencies (>98 %) under visible light irradiation. Based on experimental observations and theoretical insights, it is suggested that the higher quantum yield and photocatalytic reactivity of x-LFMO composites are attributed to the bulk oxygen mobility and surface oxygen reactivity promoted by the octahedral distortion of BO6 in LaFe0.67Mo0.33O3 and the heterogeneous structure formed at the interface of the two phases.

Electronic properties of the barium magnesium tantalate

BaMg1/3Ta2/3O3 (BMT) crystals belong to the family of complex perovskites and are well known for their excellent microwave dielectric properties. In this work, structural optimization of the lattice parameters was performed. Electron density functional theory calculations of the electronic band structure of BMT crystal of the trigonal phase were carried out along Г–A–K–M–L directions of the Brillouin zone. The calculated band gap energy was 3.554 eV. The partial density of states of BMT crystal in P-3 m1 phase was simulated. Top of the valence band was formed by 2p-states of O and bottom of the conduction band – by 5d-states of Ta.

Investigation of AcXO3 (X = Al, Ga) perovskites for energy harvesting applications: a DFT approach

Full potential linearized augmented plane wave (FP-LAPW) based computational study is presented for AcAlO3 and AcGaO3. Tolerance factor (τG) is 0.93 for AcAlO3 and 0.90 for AcGaO3 which reveal the stability of proposed perovskite oxides in cubic phase. The calculated band structures for both materials reveal the nonmagnetic semiconductive nature with energy band gaps of 3.98 and 2.75 eV for respective Al and Ga based perovskites. Total, and partial density of states (DOS) are computed for meaningful understanding of semiconducting behavior of the proposed perovskites. The partially filled O-2p and Ac-6d states are observed to lie in the vicinity of Fermi level. Furthermore, various parameters of optical spectra have also been computed to study the light matter interaction. Moreover, thermoelectric (TE) properties of both materials have been investigated by using semiclassical Boltzmann theory with constant relaxation time approximation. Calculated figure of merit (ZT) values for AcAlO3 and AcGaO3 are 0.23 and 0.20 at 800 K, respectively. Overall, computational study for titled perovskites indicate that these materials have application in UV sensors, photovoltaic and thermoelectric devices.

The Influence of Geometric Parameters for Training an Artificial Neural Network to Predict the Band Structure of 1-D Fishbone Photonic Crystal

With the rising demand for the transmission of large amounts of information over long distances, the development of integrated light circuits is the key to improving this technology, and silicon photonics have been developed with low absorption in the near-infrared range and with sophisticated fabrication techniques. To build devices that work in different functionalities, photonic crystals are one of the most used structures due to their ability to manipulate light. The investigation of photonic crystals requires the calculation of photonic band structures and is usually time-consuming work. To reduce the time spent on calculations, a trained ANN is introduced in this study to directly predict the band structures using only a minimal amount of pre-calculated band structure data. A well-used 1-D fishbone-like photonic crystal in the form of a nanobeam is used as the training target, and the influence of adjusting the geometric parameters is discussed, especially the lattice constant and the thickness of the nanobeam. To train the ANN with very few band structures, each of the mode points in the band structure is considered as a single datapoint to increase the amount of training data. The datasets are composed of various raw band structure data. The optimized ANN is introduced at the end of this manuscript.

Ab-initio insights into the physical properties of XIr3 (X = La, Th) superconductors: A comparative analysis

Here we report the structural, elastic, bonding, thermo-mechanical, optoelectronic and superconducting state properties of recently discovered XIr3 (X = La, Th) superconductors utilizing the density functional theory (DFT) using two different exchange-correlations functionals. The elastic, bonding, thermal and optical properties of these compounds are investigated for the first time. The calculated lattice and superconducting state parameters are in reasonable agreement to those found in the literature. In the ground state, both the compounds are mechanically stable and possess highly ductile character, high machinability, low Debye temperature, low bond hardness and significantly high melting point. The thermal conductivities of the compounds are found to be very low which suggests that they can be used for thermal insulation purpose. The population analysis and charge density distribution map confirm the presence of both ionic and covalent bonds in the compounds with ionic bond playing dominant roles. The calculated band structure and DOS profiles indicate metallic character of XIr3 compounds. It is also found from the DOS profile that the Ir 5d-states dominate near the Fermi level. Unlike the significant anisotropy observed in elastic and thermal properties, all the optical constants of XIr3 compounds exhibit almost isotropic behavior. The optical parameters’ profiles correspond very well with the electronic band structure and DOS features. We have estimated the superconducting transition temperature (Tc) of XIr3 compounds in this work. The calculated values of Tc for LaIr3 and ThIr3 compounds are 4.91 K and 5.01 K, respectively. We have compared and contrasted all the physical properties of XIr3 (X = La, Th) compounds in this study.

Effect and Regulation Mechanism of Post-deposition Annealing on the Ferroelectric Properties of AlScN Thin Films.

Integrating ferroelectric AlScN with III-N semiconductors to enhance the performance and tunability of nitride devices requires high-quality AlScN films. This work focuses on the effect and regulation mechanism of post-annealing in pure N2 on the crystal quality and ferroelectric properties of AlScN films. It is found that the crystal quality improves with increasing annealing temperatures. Remarkably, the leakage current of AlScN films caused by grain boundaries could be reduced by four orders of magnitude after annealing at 400 °C. The crystal growth dynamics simulations and band structure calculations indicate that the energy supplied by the temperature facilitates the evolution of abnormally oriented grains to have a better c-axis orientation, resulting in the defect states at the Fermi-level disappearing, which is mainly the reason for the leakage current decrease. More interestingly, the reduction of leakage current leads to the previously leaking region exhibiting ferroelectric properties, which is of great significance to improve the ferroelectricity of AlScN and ensure the uniformity of devices. Furthermore, annealing enhances the tensile strain on the film, which flattens the energy landscape of ferroelectric switching and reduces the coercive field. However, the risk of incorporation of oxygen will also be increased if the annealing temperatures are higher than 400 °C, which will not only reduce the relative displacement of metal atoms and nitrogen atoms in AlScN but also enhance the ferroelectric depolarization field, leading to the remnant polarization decreasing dramatically. These discoveries facilitate a deeper understanding of the influencing mechanism on the ferroelectric properties of AlScN films and provide a direction for obtaining high-quality AlScN.

Study on the double negativity in deformed single-phase chiral metamaterials under tensile loads

Elastic metamaterials with double negativity can manipulate the propagation of elastic waves at sub-wavelength scales by inducing multiple resonances to achieve different negative effective parameters. Numerous efforts have been made to control the dynamic behavior by directly tuning the frequency range of double negativity in elastic metamaterials. This study examines the impact of tensile loads on double negativity in relation to ligament inclination angle. The findings will aid in the direct tunability of double negativity in single-phase chiral metamaterials. The study examines a simple single-phase four-ligament chiral unit with low-order double negativity. The presence of double negativity was verified through band structure analysis and calculation of the four effective dynamic parameters. Additionally, the effects of two geometrical factors on the frequency ranges of negative parameters were investigated through parametric scanning. The results indicate that the frequency range of double negativity reaches its maximum at a ligament inclination angle of around 45° and disappears as the angle approaches 65°. Given that the ligament inclination angle of the unit cells can be easily altered by external tension, this intriguing outcome is leveraged to achieve the emergence and vanishing of double negativity. This characteristic is confirmed through the examination of negative refraction phenomena via simulation examples.

Investigation of lead-free direct bandgap Ca[formula omitted]MAsO[formula omitted] (M=Ga, In) double perovskites for optoelectronic and thermoelectric applications: A first principles study

In this study, an extensive investigation into the multiple characteristics of Ca2MAsO6 (M=Ga, In), double perovskite materials, focusing on their structural, mechanical, electronic, optical, and thermoelectric properties utilizing the density functional theory is explored. The structural and mechanical stability of these materials with a cubic structure is confirmed by the tolerance factors, octahedral factors, and mechanical stability assessments. Moreover, these materials exhibit an isotropic nature with high rigidity. The calculated band structures reveal that these materials exhibit a band gap of 2.61 eV for Ca2GaAsO6 and 2.83 eV for Ca2InAsO6 with direct band gap in nature. Additionally, the optical properties reveal that effective absorption takes place within the ultraviolet region in the electromagnetic spectrum. The band structure and optical properties make these materials suitable for optoelectronic applications. Finally, the calculated thermoelectric properties, namely Seebeck coefficient, electrical and thermal conductivity, and figure of merit indicate that these materials possess advantageous thermoelectric traits, further solidifying their potential candidacy for thermoelectric devices.

An efficient and unified method for band structure calculations of 2D anisotropic photonic-crystal fibers

An efficient and unified method for band structure calculations of 2D anisotropic photonic-crystal fibers