Electronic Behavior Research Articles

On the Physical Mechanisms Driving the Different Deep Penetration of Radiation Belt Electrons and Protons

AbstractDuring active geomagnetic periods both electrons and protons in the outer radiation belt have been frequently observed to penetrate to low L (<4). Previous studies have demonstrated systematic differences in the deep penetration of the two species of particles, most notably that the penetration of protons is observed less frequently than for electrons of the same energies. A recent study by Mei et al. (2023, https://doi.org/10.1029/2022GL101921) showed that the time‐varying convection electric field contributes to the deeper penetration of low‐energy electrons and that a radial diffusion‐convection model can be used to reproduce the storm‐time penetration of lower‐energy electrons to lower L. In this study, we analyze and provide physical explanations for the different behaviors of electrons and protons in terms of their penetration depth to low L. A radial diffusion‐convection model is applied for the two species with coefficients that are adjusted according to the mass‐dependent relativistic effects on electron and proton drift velocity, and the different loss mechanisms included for each species. Electromagnetic ion cyclotron (EMIC) wave scattering losses for 100s of keV protons during a specific event are modeled and quantified; the results suggest that EMIC waves interacting with protons of lower energies than electrons can contribute to prevent the inward transport of the protons.

Constraints on the spin-state transition of siderite from laboratory-based Raman spectroscopy and electrical conductivity under high temperature and high pressure

The vibrational and electrical transport properties of natural siderite are systematically investigated by means of in-situ Raman spectroscopy and alternating current impedance spectroscopy under conditions of 0.6–55.6 GPa, 298–873 K and different hydrostatic environments using a diamond anvil cell (DAC). Upon non-hydrostatic compression, all of these observable characteristic variations of siderite including the appearance of three absolutely new Raman peaks (L’, v4′ and v1′), the disappearance of Raman peaks (T, L and v4) and the discontinuity in the pressure-dependent electrical conductivity can provide robust evidence of electronic spin transitions of Fe2+ from high-spin to mixed-spin to low-spin states at the respective pressures of 42.5 GPa and 48.5 GPa. As far as hydrostatic condition, the electronic spin states from high-spin to mixed-spin to low-spin states occurred at the higher pressures of 45.7 GPa and 50.4 GPa, respectively, which implied the highly sensitive hydrostaticity of electronic spin transition pressures. Upon decompression, the reverse electronic spin transitions from low-spin to mixed-spin to high-spin states were detected at the respective pressures of 47.2 GPa and 28.7 GPa under non-hydrostatic condition, and as well as at the pressures of 49.4 GPa and 25.1 GPa under hydrostatic condition, respectively. The huge pressure hysteresis of 13.8 GPa and 20.6 GPa for the electronic spin state transition was revealed under non-hydrostatic and hydrostatic environments, respectively. In order to explore the effect of temperature on the electronic spin transition, a series of electrical conductivity experiments on siderite were performed over the temperature range of 323–873 K under conditions of three typical pressures of 47.7, 49.8 and 51.6 GPa. Furthermore, the functional relationships between the temperature and pressure describing the high-spin to mixed-spin to low-spin transitions for siderite were successfully established: P1 (GPa) = 39.318 + 0.015 T (K) and P2 (GPa) = 41.277 + 0.018 T (K), respectively. In conclusion, our acquired phase diagram of the electronic spin transition on siderite is beneficial to deep insight into the electronic spin behavior for those of iron-bearing carbonate minerals under high-temperature and high-pressure conditions.

Recent Advances in Direct Regioselective C-H Chlorination at Aromatic and Aliphatic.

Direct installation of key functionalities in a molecule through C-H bond activation is one of the thrust areas as well as challenging task in organic synthesis. Particularly, introduction of chlorine in a molecule imparts additional benefits for further functionalizations as well as improves the electronic behaviour such as lipophilicity and polarity towards drug development process. The chlorinated molecules have also been established as efficient biologically relevant scaffolds. Current manuscript has been focused on the direct installation of the chlorine atom at various aromatic and aliphatic positions to produce functional molecules. The key highlight of the manuscript belongs to the site selectivity (regioselectivity) for the installation of chlorine functionality. Manuscript describes the advanced methods developed for the direct C-H chlorination reactions and further simplified for the chlorination reactions at various positions including aromatic (o-, m-, and p-), benzylic, heteroaromatic, and aliphatic positions. Directing groups (DGs) and the coordination with the catalyst is the key for the enhancement of regioselectivities during direct C-H chlorination reactions.

Exploring Structural, Electronic, Vibrational, and Thermophysical Properties of Fe–Pt, Fe3–Pt, and Fe–Pt3 Alloys: A Density Functional Theory Study

Utilizing density functional theory, the structural, electronic, vibrational, and thermophysical properties of L10 FePt, L12 Fe3Pt, and L12 FePt3 alloys are meticulously analyzed. Employing projected augmented wave pseudopotentials alongside the Perdew–Burke–Ernzerhof exchange‐correlation function, equilibrium lattice constants are computed, aligning closely with existing data, thus validating our approach. To ascertain the dynamical stability of these alloys, phonon frequencies and density of states across high symmetry directions of the Brillouin zone are computed, affirming their stability with positive phonon frequencies throughout. Furthermore, the electronic band structure, the total and projected density of states, electronic charge density, and Fermi surfaces of the alloys are delved. The thorough analysis of phonon dispersion curves, electronic band structures, and the density of states, charge densities, and Fermi surfaces provides conclusive insights into the properties and behavior of the alloys. In essence, comprehensive investigation offers valuable insights into the thermophysical properties of L10 FePt, L12 Fe3Pt, and L12 FePt3 alloys, spanning equilibrium lattice constants, phonon characteristics, and electronic properties. These findings significantly augment the understanding of the structural stability, phonon dynamics, and electronic behavior exhibited by these alloys.

From lithium and sodium superoxides to singlet-oxygen - insights into the mechanism of dissociation using SHARC-MD.

The parasitic formation of singlet oxygen in aprotic alkaline/air batteries presents a challenge for the technical development of these systems. Avoidance strategies and investigation of reaction paths such as disproportionation of LiO2 and NaO2 have been presented. Furthermore, the dissociation of these superoxide systems have been discussed be as an alternative reaction channel. Here, we present a fundamental study of the electronic nature and dissociation behaviour of the alkali superoxides. The molecular systems were calculated at the CASSCF/CASPT2-level of theory. We determined the minimum energy crossing points along the dissociation required to form 3O2 and 1O2. Building on these results, a surface-hopping AIMD-simulation was performed employing the SHARC program package to follow the electronic transitions along the minimum energy crossing pooints during the dissociation. The feasibility of populating the electronic state corresponding to the formation of singlet oxygen during dissociation was demonstrated. For LiO2, 6.85% of the trajectories were found to terminate under formation of 1O2, whereas for NaO2 only 1.68% of the trajectories ended up in 1O2 formation. This represents an inverse trend to that reported in the literature. This observation suggests that the dissociation is a viable, monomolecular reaction path to 1O2 that complements the disproportionation pathway.

Thickness-modulated electronic band structures and exciton behavior of non-van-der-waals 2D Bi2O2Se films

Bi2O2Se, as a non-van-der-waals (non-vdW) interlayer coupling two-dimensional material, its electronic band structures and exciton behavior still merit further in-depth studies, especially in the consideration of thickness tuning degrees of freedom. Here, we reveal the broadband excitonic performance and critical point properties of Bi2O2Se films with different thicknesses (3.54–16.33 nm). Five critical points are determined and assigned to specific optical transitions. Moreover, we observe that electronic bandstructures in the Γ valley are stable with variable thicknesses, while the deeper electron levels received more pronounced thickness modulation. And we first report four excitons in wide spectral range (1.24–6.20 eV) through absorption coefficient fitting. Significantly, due to the strong localization of electrons and holes induced by the intralayer built-in electric field, the exciton binding energy (Eb) value of 3.54 nm-Bi2O2Se (234 meV at Γ position) is apparently larger than typical multi-layer TMDCs, which offering unprecedented opportunities in applications in optoelectronic devices. Furthermore, Eb of two excitons at low energy region (Eb1, Eb2) red-shift with increasing thickness, while Eb of higher-energy excitons (Eb3, Eb4) blue-shift, owing to the dispersion characteristic of the effect dielectric screening effects. Our results are vital to wide-ranging applications of Bi2O2Se from fundamental science to optoelectronic devices.

Strain-bandgap quasi-linear correlation applied to modulation of NiBr2 monolayer optical properties

Recently, two-dimensional transition metal dihalides have shown diverse applications in spintronics, quantum devices, and optoelectronic devices. In this work, density functional theory (DFT) is adopted to investigate the effect of biaxial strain upon the electronic structure and optical properties of NiBr2 monolayer. The results show that NiBr2 is an indirect semiconductor with band gap 2.62 eV (DFT + U) and 3.18 eV (HSE06), which could vary quasi-linearly from 2.73 eV to 1.71 eV modulated by biaxial strain (6 % to −10 %). Combined with the analysis of the density of states (DOS), the primary reason for the alteration in the band gap is that strain significantly affects the behavior of Ni 3d electrons. When the strain changes from positive to negative, the DOS of Ni 3d shifts towards the Fermi level, resulting in a reduction in the band gap. Within this strain range, all of the optical properties exhibit a quasi-linear tendency similar to the band gap variation. The optical peaks of NiBr2 under compressive strain are not only red-shifted into the visible light (VL) region but also significantly enhanced in the VL and ultraviolet (UV) regions. Applying strain can greatly boost the electrical and optical properties of NiBr2 monolayer, making it a promising candidate in the field of ultraviolet detectors.

Mechanism of the Terahertz Wave-MXene Interaction and Surface/Interface Chemistry of MXene for Terahertz Absorption and Shielding.

ConspectusOver the past two decades, terahertz (THz) technology has undergone rapid development, driven by advancements and the growing demand for THz applications across various scientific and technological domains. As the cornerstone of THz technology, strong THz-matter interactions, especially realized as high THz intrinsic absorption in nanometer-thick materials, play a highly important role in various applications including but not limited to THz absorption/shielding, detection, etc. The rigorous electromagnetic theory has posited a maximum intrinsic absorption of 50% for electromagnetic waves by thin films, and the succinct impedance matching condition has also been formulated to guide the design of highly intrinsically absorbing materials. However, these theories face challenges when applied to the THz spectrum with an ultrabroad bandwidth. Existing thin films typically achieve a maximum intrinsic absorption within a narrow frequency range, significantly limiting the performance of THz absorbers and detectors. To date, both theoretical frameworks and experimental solutions are lacking in overcoming the challenge of achieving broadband maximum intrinsic absorption in the THz regime.In this Account, we describe how two-dimensional (2D) transition-metal carbide and/or nitride (MXene) films with nanometer thickness can realize the maximum intrinsic absorption in the ultrabroad THz band, which successfully addresses the forementioned longstanding issue. Surprisingly, traditional DC impedance matching theory fails to explain this phenomenon, while we instead propose a novel theory of AC impedance matching to provide a satisfactory explanation. By delving into the microscopic transport behavior of free electrons in MXene, we discover that intraflake transport dominates terahertz conductivity under THz wave excitation, while interflake transport primarily dictates DC conductivity. This not only elucidates the significant disparities between DC and AC impedance in MXenes but also underscores the suitability of AC impedance matching for achieving broadband THz absorption limits. Furthermore, we identify a high electron concentration and short relaxation time as crucial factors for achieving broadband maximum absorption in the THz regime. Although approaching the THz intrinsic absorbing limits, it still faces hurdles to the use of MXene in practical applications. First, diverse and uncontrollable terminations exist on the surface of MXene stemming from the synthesis process, which largely influence the electron structure and THz absorbing property of MXene. Second, MXene suffers from poor stability in the presence of oxygen and water. To address the above issues, we have undertaken distinctive works to precisely control the terminations and suppress the oxidation of MXene even at high temperature through surface and interface chemistry, such as low-temperature Lewis basic halide treatment and building a Ti3C2Tx/extracted bentonite (EB) interface. For practical application consideration, we proposed a copolymer-polyacrylic latex (PAL)-based MXene waterborne paint (MWP) with a strong intermolecular polar interaction between MWP and the substrate provided by the cyano group in PAL. This not only has strong THz EMI shielding/absorption efficiency but also can easily adhere to various substrates that are commonly used in the THz band. These studies may have significant implications for future applications of MXene nanofilms in THz optoelectronic devices.

Synthesis, physico-chemical characterization, DFT simulation, and field electron behaviour of 2D layered Ti3C2Tx MXene nanosheets

Nanostructures of Ti3C2Tx, one of the members of the MXenes family, have been successfully prepared by chemical etching of Al from Ti3AlC2 (MAX phase) using Hydrofluoric Acid (HF) for various etching durations at room temperature. The phase, morphological, structural, and chemical analysis was performed using XRD, FESEM, TEM, Raman, and x-ray photoelectron spectroscopy. The surface morphology of as-synthesized Ti3C2Tx (MXene) phase is characterized by stacks of layered sheets like structures. Field electron emission (FEE) behaviour was investigated at the base pressure of 1 × 10−8 mbar. The pristine Ti3AlC2 (MAX) and Ti3C2Tx (MXene) nanosheets emitters showed values of turn-on field (defined at current density ∼ 1 μA cm−2) as 4.18 and 1.67 V μm−1, respectively. Furthermore, maximum emission current density of ∼ 825 μA cm−2 was extracted from the MXene nanosheets emitter at an applied field of 3.60 V μm−1, in contrast to ∼71 μA cm−2 drawn at 7.31 V μm−1 from the pristine MAX emitter. The MXene nanosheets emitter exhibited good emission current stabilities at pre-set values ∼ 10 and 100 μA over 3 h duration. Work function values of the MAX and MXene nanosheets emitters were measured using a retarding field analyzer, and found to be 4.4 and 3.6 eV, respectively. Extensive ab-initio simulations have been performed to provide structural and electronic properties, as well as for estimating the work function of Ti3C2 layered material. The estimated electronic density of states revealed its metallic character. The improved FEE performance exhibited by the 2D layered Ti3C2Tx (MXene) nanosheets emitter is attributed to its unique morphology characterized by high aspect ratio, metallic electronic properties and relatively lower work function.

Investigation of numerical transport models in protein-based molecular junctions with cofactors of diverse chemical natures

The cofactors of proteins dictate the charge transport mechanism across molecular junctions when self-assembled protein monolayers are sandwiched between two metal electrodes. Here, we summarized how the chemical coordination nature of cofactors in various proteins modulates electrical conductance by investigating electronic transport studies across different protein-based molecular junctions under various forces applied under the AFM tip. We have utilized several numerical techniques of electronic transport to analyse the experimentally obtained current–voltage measurements across various protein-based molecular junctions and depicted the origin of electronic modulation in the electrical conductance under different external stimuli. We could also find the origin of electronic conductance modulation under external stimuli at various applied forces by obtaining several analytical transport parameters such as energy barrier, coupling strength, and electrical conductance values. Utilizing density-functional-theory calculations, we further validate that the electronic density of states present in the cofactors within the proteins dominates the electronic transport behaviours across protein-based molecular junctions. Our findings reveal the limiting factor for applying various external stimuli on different proteins, which could be further valuable in bioelectronic applications. We have also found that the organic cofactor containing protein follows all the tunneling mechanism-related numerical transport models and the electronic transport across proteins with pure inorganic cofactors follows Landauer transport formalism.

Topological structures and adsorption properties of the [Fe4S4] clusters

The [Fe4S4] compositions are ubiquitous in biological systems as integral parts of the complex catalytic mechanisms as in hydrogenases and nitrogenases. The current reports about [Fe4S4] species are based on the cube-like structure framework. Here, the topological structures, stability and electronic properties of gas phase [Fe4S4]+, [Fe4S4]0 and [Fe4S4]− are analyzed. It is found that ground state structures of these three clusters have similar cubic cages but different symmetries and spin multiplicities. The molecular dynamics simulations demonstrate that the cubic cage remains thermodynamically stable at 700 K. The density of states show that the charge state is the key to affect electronic behaviors of them even under the same structural framework. The molecular orbitals show that the LUMO orbitals are distributed throughout whole structures, showing great delocalized characteristics, especially for the anionic [Fe4S4]−, while the HOMO orbits are mainly localized in Fe-S bonds, which are also confirmed by the electron localization function analyses. After one CO molecule is adsorbed on these clusters, it prefers to locate at the Fe atoms. Moreover, the C–O bond length and vibration frequency of the [Fe4S4]−-CO undergone a significant red shift. Our work shows that the [Fe4S4]− may act as a potential catalyst for activating the C–O bond.

Investigation of the electronic properties of a topological semimetal LaAuPb under uniaxial strain and hydrostatic pressure: A DFT approach

In this study, we utilized first-principles calculations to investigate the structural, electronic, mechanical, and vibrational properties of the topological semimetal LaAuPb. Our research delves into how uniaxial strain and hydrostatic pressure influence the electronic band structure of LaAuPb. We discovered that LaAuPb exhibits ductile behavior and maintains dynamic stability under various conditions. Upon introducing compressive strains of −6%, we observed a significant separation of degenerate states at the gamma point, which consequently led to the formation of a band gap. Similarly, the application of hydrostatic pressure at 16 GPa also resulted in the creation of a band gap by altering the electronic band structure. These findings suggest that both compressive strain and hydrostatic pressure can be effective in modulating the electronic properties of LaAuPb, potentially making it useful for applications requiring tunable electronic behavior. Conversely, when subject to tensile strain, no band gap formation was observed. Instead, there was a notable gradual overlap between the valence and conduction bands, indicating that tensile strain does not induce the same electronic separations as compressive strain or hydrostatic pressure. This asymmetrical response to different types of strain underscores the complex nature of LaAuPb's electronic properties and provides valuable insights for its potential use in electronic and mechanical applications. Overall, our findings contribute to the understanding of how external mechanical forces can be harnessed to control the electronic properties of topological semimetals like LaAuPb.

Theoretical perspectives on the electronic, optical, mechanical, magnetic, and anisotropic behaviors of the quaternary Heusler alloys RhFeMnZ and IrMnCrZ (where Z = Si, Ge)

High-spin-polarised materials are the most promising candidates for spintronic devices. Here, the spin-polarised electronic structure, magnetism, mechanical, and optical properties of RhFeMnZ and IrMnCrZ (where Z = Si, Ge) Quaternary Heusler alloys were calculated by first-principles calculations. The calculations show that type III for the RhFeMnSi, RhFeMnGe, and IrMnCrSi and type I for the IrMnCrGe compound configuration is the most stable crystal structure for the studied alloys. The four alloys were found to have a half-metallic ferromagnetic structure with indirect band gaps in the majority spin channels of 0.957, 0.66, 0.745, and 0.891 eV for RhFeMnSi, RhFeMnGe, IrMnCrSi, and IrMnCrGe, respectively. They exhibit an appreciable total magnetic moment of 4 μB for RhFeMnZ (Z = Si, Ge) and 2 μB for IrMnCrZ (Z = Si, Ge). The results show that RhFeMnZ and IrMnCrZ (where Z = Si, Ge) are ferromagnetic half-metals with 100 % spin polarisation. The results of the elastic constants demonstrate the mechanical stability of RhFeMnZ and IrMnCrZ (where Z = Si, Ge) alloys. Optical properties such as dielectric function, absorption, reflectance, optical conductivity, and other optical properties were also probed. In the ultraviolet region, RhFeMnZ and IrMnCrZ (where Z = Si, Ge) are effective absorbers and have a high refractive index. Alloys are promising candidates for potential applications in spintronic devices.

The electronic, magnetic, and optical behaviors of graphyne modulated by metal atoms adsorption: a first-principles study

The electronic, magnetic, and optical behaviors of graphyne modulated by various adsorbed metal atoms (Li, Na, K, Mg, Ca, Al, and Zn) from typical metal-ion batteries are studied by first-principles calculation. Notably, Mg and Zn adsorption systems are deemed unstable. In contrast, Li, Na, K, Ca, and Al systems exhibit two preferential adsorption sites, with the optimal position being the hollow center site within the large acetylenic ring. Upon the adsorption of these metal atoms, except for Ca adsorption systems exhibit semi-metallic behavior, while the other metal adsorption systems induced a transition from p-type to n-type semiconductors with decreased band gaps. Intriguingly, the inherent magnetism of the metal atoms vanished, resulting in a total magnetic moment of 0 μ B for the adsorption systems. Furthermore, the optical absorption and reflectivity peak positions for Ca adsorption systems show a significant redshift from violet to green and blue light regions. Conversely, other adsorption systems exhibit new absorption and reflection peaks in the infrared range, accompanied by an increase in both absorption coefficient and reflectivity across various spectral regions. These findings are conducive to the application in the field of novel optoelectronics and optical films.

Electronic and thermoelectric behaviour of XCaB (X = Li, Na, K) half-Heusler alloys under strain

Impact of isotropic strain (≤±10 %) on electronic and thermoelectric properties of XCaB (X = Li, Na, K) half-Heusler alloys is studied using DFT method. LiCaB possesses the maximum structural, dynamical and mechanical stability among the considered alloys. The alloys remain ferromagnetic and most of them also retain half-metallicity even in strained conditions. Inclusion of lattice thermal conductivity (κl) lowers the total figure of merit (ZTtot) to almost half (∼0.6 at 800K) of that of electronic figure of merit (ZTel) (∼1 at 200K). Ductility detests κl but favours ZTtot. Application of strain could tune electronic band structure and/or mechanical behaviour of LiCaB, KCaB increasing ZTtot to about 0.75, 0.67, respectively, at relatively larger compressive strains, except for a negligible change in NaCaB. Thus, required modifications in electronic and mechanical properties of XCaB alloys are beneficial for thermoelectric performance and can be achieved under appropriate strain application.

Geometric properties of the first singlet S-wave excited state of two-electron atoms near the critical nuclear charge

Abstract In this work the geometric structure parameters and radial density distribution of 1s2s 1 S excited state of the two-electron atomic system near the critical nuclear charge Z c were calculated in detail under tripled Hylleraas basis set. Contrary to the localized behavior observed in the ground and the doubly excited 2p 2 3 P e states, for this state our results identify that while the behavior of the inner electron increasingly resembles that of a hydrogen-like atomic system, the outer electron in the excited state exhibits diffused hydrogen-like character and becomes perpendicular to the inner electron as nuclear charge Z approaches Z c. This study provides insights into the electronic structure and stability of the two-electron system in the vicinity of the critical nuclear charge.

Exploring Social Media and E-Communication Patterns Among Indigenous Youth in Sri Lanka

Social media and other digital technology use has skyrocketed in Sri Lanka and around the world, especially among marginalized youth groups like Indigenous communities. This study delves into the intricate interplay of social media and electronic communication (E-communication) patterns within the context of indigenous youth in Sri Lanka. As globalization and technological advancements continue to reshape traditional sociocultural landscapes, indigenous communities find themselves navigating an evolving digital terrain. this study aims to elucidate the patterns of engagement among this demographic, focusing on their preferences and behaviors in the digital realm. This paper examines the published literature to learn about how Indigenous youth in Sri Lanka use digital technologies and social media, as well as the positive and negative effects this has on their lives. This quantitative study on Sri Lanka's indigenous youth employed simple random sampling and an online questionnaire survey with 110 respondents, revealing insights into their social media and electronic communication behaviors, and was conducted using a descriptive research design and a sample of 36 respondents. The research findings suggest that even though the indigenous youth have less access to social media and digital technology, there are many ways social media affects their daily activities. growing the population and other advancements have increased the usage of social media and other devices among the youth indigenous population in Sri Lanka. It is anticipated that the findings will provide valuable insights for scholars, policymakers, and community leaders, fostering a more holistic approach to digital inclusion that respects the unique needs and aspirations of indigenous youth in Sri Lanka.

Superlubric Sliding of Graphene Auto-Kirigami with Interfaces Containing Self-Assembled Stripe-Pattern Adsorbates.

Van der Waals heterostructures formed by stacked 2D materials show exceptional electronic, mechanical, and optical properties. Superlubricity, a condition where atomically flat, incommensurate planes of atoms result in ultra-low friction, is a prime example enabling, for example, self-assembly of optically visible graphene nanostructures in air via a sliding auto-kirigami process. Here, it is demonstrated that a subtle but ubiquitous adsorbate stripe structure found on graphene and graphitic surfaces in ambient conditions remains stable within the interface between twisted graphene layers as they slide over each other. Despite this contamination, the interface retains an exceptional superlubricious state with an estimated upper bound frictional shear strength of 10kPa, indicating that direct atomic incommensurate contact is not required to achieve ambient superlubricity for 2D materials. The results suggest that any phenomena depending on 2D heterostructure interfaces such as exotic electronic behavior may need to consider the presence of stripe adsorbate structures that remain intercalated.

Spin-polarized electronic, optical, and transport properties of novel Cs2XMoBr6 (X=Na, Li) HDPs: First-principles study

We explored the electronic, optical, and thermoelectric characteristics of novel Cs2XMoBr6 (X=Na, Li) halide-based double perovskites (HDPs) in their monoclinic phase using the density functional theory (DFT). The full-potential linearized augmented plane wave approach was used in the present work. The material Cs2NaMoBr6 was noticed as half-metallic as indicated by an indirect band gap semiconducting nature in the spin-down channel, and with a metallic nature in the spin-up channel. Similarly, the Cs2LiMoBr6 material also revealed a half-metallic nature with an indirect band gap semiconducting nature in spin-down mode and a metallic behavior in spin-up mode. The density of states analysis verifies the electronic behavior of these compounds. To determine the optical characteristics, the optical parameters such as the dielectric functions, the absorption coefficients, the refractivity, the energy loss function, and the reflectivity, have been described. The thermoelectric characteristics of the compounds along the temperature are calculated. It was confirmed that these materials possess extraordinary characteristics that would make them excellent options for influential electronic, optical, and thermoelectric, device applications.

First-principles calculation to investigate phase transition and associated changes in electronic, excitonic, and optical behavior of RbMgH3 perovskite polymorphs

Motivated by recent experimental and theoretical research on the ability to store and release hydrogen from a hydride perovskite with a large ionic character called RbMgH3, we conducted a study using density functional theory (DFT) to investigate the optoelectronic behavior of RbMgH3 in both Cubic and Hexagonal structures, as well as its phase transition.Our findings reveal that RbMgH3 exhibits an indirect band gap of 2.41 eV in the Hexagonal phase and a direct band gap of 2.15 eV in the Cubic phase. Additionally, we calculated the Gibbs energy to predict the occurrence of the phase transition. It was determined that RbMgH3 undergoes a structural transformation from Cubic to Hexagonal at a pressure of 1.78 GPa. This transition has the potential to enhance the storage kinetics of hydrogen, making RbMgH3 suitable for various applications.