Energy Range Research Articles

Phase change material microcapsules doped with phosphorus-based flame retardant filled titanium dioxide nanotubes for enhancing the energy storage and temperature regulation performance of buildings

Solar energy is not only a green alternative to fossil energy but also a candidate for future mainstream energy sources. To improve the efficiency and application range of solar energy, we investigated tris (1-chloro-2-propyl) phosphate (TCPP) modified titanium dioxide nanotubes (TNTs) doped phase change material microcapsules (p-t-MPCMs) to enhance the temperature regulation and flame retardancy of epoxy resin (EP) coatings. Transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectroscopy determined the successful preparation of p-TNTs and p-t-MPCMs. Moreover, it was confirmed that the p-t-MPCMs had great thermal stability and reliability by the thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The p-t-MPCMs increased residual mass by 12.2 % at 600 ℃ while correcting the initial melting temperature of MPCMs by 1.0 ℃. Based on the principle of oxygen consumption, the heat release rate (HRR) of EP coatings containing the p-t-MPCMs (p-t-MPCM/EP) was reduced from 665.92 kW/m2 to 443.78 kW/m2, resulting in a total heat release reduction (THR) of 17.73 % tested by a conical calorimeter. Then the results of the miniature chamber model demonstrated that p-t-MPCM/EP had outstanding temperature control ability. In summary, the p-t-MPCMs expressed great potential in regulating building temperature timely and improving the fire safety of EP coatings.

Coulomb effect on elastic electron scattering by hydrogen atom and hydrogen-like ions in their metastable 2s state in the 511–770 KeV energy range

This paper reports on a study investigating the elastic scattering of hydrogen atoms in their metastable state (2S-2S) when subjected to electron impact, with a focus on the Coulomb effect within an energy range spanning from 511 keV to 770 keV . The analysis employs semi-relativistic wave functions to depict the hydrogen states. The validity of using Darwin wave functions is confirmed by ensuring that the condition Zα << 1 is met, where α represents the structure constant. Both incident and scattered free electrons are described using Dirac spinors. Notably, the semi-relativistic calculations converge with those of the non-relativistic case at low electron velocities. Additionally, in the presence of the Coulomb effect, the electron wave function is approximated by a Dirac function modulated by the confluent hypergeometric function. The paper presents the relativistic differential cross-section (RDCS) as a function of the final scattering angle for various energies of the incident electron, revealing intriguing insights into diffusion probabilities in specific directions. Moreover, the impact of the atomic number Z on the elastic scattering of hydrogen atoms and hydrogen-like ions by electron impact under the influence of the Coulomb effect is thoroughly examined.

Mixed quantum/classical theory (MQCT) approach to the dynamics of molecule-molecule collisions in complex systems.

We developed a general theoretical approach and a user-ready computer code that permit study of the dynamics of collisional energy transfer and ro-vibrational energy exchange in complex molecule-molecule collisions. The method is a mixture of classical and quantum mechanics. The internal ro-vibrational motion of collision partners is treated quantum mechanically using a time-dependent Schrödinger equation that captures many quantum phenomena including state quantization and zero-point energy, propensity and selection rules for state-to-state transitions, quantum symmetry and interference phenomena. A significant numerical speed up is obtained by describing the translational motion of collision partners classically, using the Ehrenfest mean-field trajectory approach. Within this framework a family of approximate methods for collision dynamics is developed. Several benchmark studies for diatomic and triatomic molecules, such as H2O and ND3 collided with He, H2 and D2, show that the results of MQCT are in good agreement with full-quantum calculations in a broad range of energies, especially at high collision energies where they become nearly identical to the full quantum results. Numerical efficiency of the method and massive parallelism of the MQCT code permit us to embrace some of the most complicated collisional systems ever studied, such as C6H6 + He, CH3COOH + He and H2O + H2O. Application of MQCT to the collisions of chiral molecules such as CH3CHCH2O + He, and to molecule-surface collisions is also possible and will be pursued in the future.

Pressure effects on the structural, electronic, elastic, optical, and vibrational properties of YMg intermetallic compounds: a first-principles study

The properties of YMg in B2 structure have been comprehensively analysed using the first-principles plane-wave pseudopotential method. Specifically, the structural, electronic, elastic, vibrational, and optical properties were investigated using the generalized gradient approximation (GGA) method in the context of density functional theory. The Vienna ab initio simulation package (VASP) was utilized for these calculations. The computed lattice parameter (3.803 Å) and bulk modulus (41.33 GPa) are consistent with the earlier data on ambient pressure. The electronic band structure and energy-dependent density of states reveal the metallic nature of the titled compounds. The Born stability requirements confirmed the mechanical stability. The analysis of Pugh’s and Poisson’s ratios and Cauchy’s pressure reveals that YMg is ductile under the pressures in consideration. According to several anisotropy indices, the compound is noticeably anisotropic both in ambient and under pressure. Our investigation includes an analysis of several fundamental mechanical parameters of the material, including the bulk modulus, the pressure derivative of the Zener anisotropy factor, Poisson’s ratio, isotropic shear modulus and Young’s modulus with a particular focus on their dependence on pressure. We have determined that the elastic constants obtained remain mechanically stable, satisfying the Born Stability conditions even at high pressures of up to 60 GPa. To explore the dynamic stability of YMg, we analysed the material’s phonon dispersion curves. The examined compound displays stability under dynamic conditions from 0 GPa to 30 GPa, as evidenced by its positive vibration frequencies. However, this stability is not sustained under higher pressure, as the compound becomes unstable after 30 GPa to 70 GPa. The electronic band structure and density of states diagrams demonstrate YMg’s metallic properties. At atmospheric pressure (0 GPa), the total density of states (TDOS) near the Fermi level is approximately 1.63 states/eV, with pressure application reducing DOS. The dielectric function, refractive index, and energy loss spectra are examined within the 0–20 eV energy range. YMg exhibits its highest absorption between 4 and 11 eV. The peak optical conductivity is observed around 0.78 eV (equivalent to 1589.5409 nm), while the most significant energy loss occurs at 11.90 eV, roughly corresponding to 2.8 Hz in the ultraviolet spectrum. Moreover, we extensively analyzed the material’s phonon thermodynamic and optical properties, providing insights into its behavior under various conditions. The outcomes acquired at zero pressure are generally coherent with the current theoretical values.

Constraining the physical parameters of XTE J1701−462 through NuSTAR observations

Abstract The spectral properties of the transient neutron star low mass X-ray binary XTE J1701−462 were studied using the data obtained from FPMA/B detectors onboard NuSTAR during its second known outburst (2022 September). The physical parameters of the system were derived from the analysis of the data in the 3.0−30.0 keV energy range. The patterns displayed on the hardness-intensity diagram of the three observations closely resembled the banana branch/normal branch, a vertex of horizontal and normal branch of the Z track and a transition from normal branch to flaring branch. Spectral analysis of the source revealed the presence of Fe K emission complex. The source spectra were fitted with a multi-temperature black body ($\mathtt {diskbb}$) component in conjunction with the reflection model ($\mathtt {relxillNS}$). The values of temperature (kTin) and radius (Rin) of the inner accretion disc obtained from the spectral fitting with the model combination - $\mathtt {constant} \times \mathtt {tbabs} (\mathtt {diskbb}$+$\mathtt {relxillNS})$ showed the source to be in its soft spectral state during the observations. The inclination angle (θ) of the source was estimated to be between 19 − 33○ and the inner disc radius (Rin) was found to be 17.4 km. Assuming the case of magnetic truncation of accretion disc, the upper limits for the magnetic dipole moment (μ) and the magnetic field strength (B) at the poles of the neutron star in the system were found to be 5.78 × 1026 G cm3 and 8.23 × 108 G, respectively, for kA = 1.

High-Performance Hard X-Ray Imaging Detector Using Facet-Dependent Bismuth Vanadate.

Bismuth vanadate (BiVO4) exhibits large absorption efficiency for hard X-rays, which endows it with a robust capacity to attenuate X-ray radiation across a broad energy range. The anisotropic properties of BiVO4 allow for the manipulation of their physical and chemical characteristics through crystallographic orientation and exposed facets. In this study, the issue of heavy recombination caused by sluggish electron transport in BiVO4 is successfully addressed by enhancing the abundance of the (040) crystal face ratio using a Co2+ crystal face exposure agent. The facet-dependent modifications exhibit excellent and balanced intrinsic charge transport properties, and finely optimize both the sensitivity and detection limit of BiVO4 X-ray detectors. As a result, ultra-stable BiVO4 metal oxide X-ray detectors demonstrate a high sensitivity of 3164 µC Gyair -1 cm-2 and a low detection limit of 20.76 nGyair s-1 under 110 kVp hard X-rays, establishing a new benchmark for X-ray detectors based on polycrystalline Bi-halides and metal oxides. These findings highlight the significance of crystal orientation in optimizing materials for X-ray detection, setting a new sensitivity record for X-ray detectors based on polycrystalline Bi-halides and metal oxides, which paves the way for the development of advanced, low-dose, and highly stable imaging systems specifically for hard X-rays.

CdTe XG-Cam: A new high-resolution x-ray and gamma-ray camera for studies of the pharmacokinetics of radiopharmaceuticals in small animals.

The recent emergence of targeted radionuclide therapy has increased the demand for imagers capable of visualizing pharmacokinetics in developing radiopharmaceuticals in the preclinical phase. Some radionuclides emit hard x-rays and gamma-rays below 100 keV, in which energy range the performance of conventional NaI scintillators is poor. Multipinhole collimators are also used for small animal imaging with a good spatial resolution but have a limited field of view (FOV). In this study, a new imager with high sensitivity over a wide FOV in the low-energy band ( 100 keV) was developed for the pharmacokineticstudy. We developed an x-ray and gamma-ray camera for high-resolution spectroscopy, named "CdTe XG-Cam," equipped with a cadmium telluride semiconductor detector and a parallel-hole collimator using a metal 3D printer. To evaluate the camera-system performance, phantom measurements with single and dual nuclides ( , , and were performed. The performance for in vivo imaging was evaluated using tumor-bearing mice to which a nuclide ( or administered. We simultaneously obtained information on and , which emit emission lines in the low-energy band with peak energies close to each other (23-26 keV for and 27-31 keV for , and applied an analytical method based on spectral model fitting to determine the individual radioactivities accurately. In the small animal imaging, the distributions of the nuclide in tumors were accurately quantified and time-activity curves in tumors areobtained. The demonstrated capability of our system to perform in vivo imaging suggests that the camera can be used for applications of pharmacokineticsresearch.

First-principles study of Na2AgAsZ6 (Z = F, Cl, Br, I) of structural, elastic, optoelectronic, and transport properties of lead-free halide double perovskites for energy conversion applications

In this article, density functional theory (DFT) is used to investigate the physical aspects of the halide double perovskites Na2AgAsZ6 (Z = F, Cl, Br, I). These substances have a cubic arrangement and are classified under space group Fm3m (225) based on their octahedral and tolerance factors values. All the perovskites are determined to be thermodynamically stable, as indicated by their negative formation energy. These double perovskite materials are semiconductors based on their electronic band structure. The energy band gaps of Na2AgAsF6, Na2AgAsCl6, Na2AgAsBr6, and Na2AgAsI6 were determined to be 2.96 eV, 1.93 eV, 1.28 eV, and 0.68 eV, respectively. We also calculated and examined the optical properties of these substances in the photon energy range of 0–8 eV. Our results indicate that the majority of the absorption occurs in the visible-ultraviolet spectrum, which makes the materials well-suited for solar systems. We employed the BoltzTraP algorithm to compute the thermoelectric properties of the materials and establish their thermoelectric behavior. These materials demonstrated figures of merit values of 0.55, 0.71, 0.74, and 0.75, respectively. Thus, these materials are appropriate for application in photovoltaic and thermoelectric devices.

First-principles study on the structural, elastic, electronic, optical and thermophysical properties of NaNO3 and K-doped NaNO3

The current work illustrates the optical, thermophysical, electronic, elastic, and structural characteristics of pure and K-doped NaNO3 obtained using DFT calculations. Electronic characteristics such as band structure, projected and total density of states of pure and doped NaNO3 are analyzed where the calculated band gaps for pure and K-doped NaNO3 were discovered to be 3.05 eV and 2.90 eV, respectively. The Berry–phase calculations carried out on both systems showed the existence of ferroelectric polarization, where an enhanced spontaneous polarization value of 36 μC/cm2 for K-doped NaNO3, as compared to 20 μC/cm2 for intrinsic NaNO3 is obtained. The thermophysical properties such as bulk modulus (B0), Debye temperature (θ D), and specific heat capacity (Cv) were calculated over a wide temperature range from 0 K to 800 K. The linear optical properties namely the dielectric constant, refractive index, electron energy loss function, absorption and extinction coefficient are calculated in wide energy range from 0 to 30 eV and discussed in detail.

Impact of nuclear effects on the ultrafast dynamics of an organic/inorganic mixed-dimensional interface

Abstract Electron dynamics at weakly bound interfaces of organic/inorganic materials are easily influenced by large-amplitude nuclear motion. In this work, we investigate the effects of different approximations to the equilibrium nuclear distributions on the ultrafast charge-carrier dynamics of a laser-excited hybrid organic/inorganic interface. By considering a prototypical system consisting of pyrene physisorbed on a MoSe2 monolayer, we analyze linear absorption spectra, electronic density currents, and charge-transfer dynamics induced by a femtosecond pulse in resonance with the frontier-orbital transition in the molecule. The calculations are based on \textit{ab initio} molecular dynamics with classical and quantum thermostats, followed by time-dependent density-functional theory coupled to multi-trajectory Ehrenfest dynamics. We impinge the system with a femtosecond (fs) pulse of a few hundred GW/cm2 intensity and propagate it for 100 fs. We find that the optical spectrum is insensitive to different nuclear distributions in the energy range dominated by the excitations localized on the monolayer. The pyrene resonance, in contrast, shows a small blue shift at finite temperatures, hinting at an electron-phonon-induced vibrational-level renormalization. The electronic current density following the excitation is affected by classical and quantum nuclear sampling through suppression of beating patterns and faster decay times. Interestingly, finite temperature leads to a longer stability of the ultrafast charge transfer after excitation. Overall, the results show that the ultrafast charge-carrier dynamics are dominated by electronic rather than by nuclear effects at the field strengths and time scales considered in this work.

КОНФОРМАЦИОННЫЕ СВОЙСТВА И ЭЛЕКТРОННАЯ СТРУКТУРА ПРОТИВООПУХОЛЕВОГО АГЕНТА TYR-SER-LEU

Molecular modeling methods were used to study the features of the spatial and electronic structure of the antitumor tripeptide YSL (Tyr-Ser-Leu), developed by Chinese scientists. The conformational analysis of the molecule revealed a limited set of its energetically preferable conformational states in a certain range of relative energy. The nature of the forces stabilizing the low-energy conformations of the tripeptide molecule was determined. As a result of the study, the energetically preferable ranges of dihedral angles, the energy contributions of interresidual interactions and hydrogen bonds, as well as the mutual arrangement of residues and their side chains in low-energy conformations of the tripeptide were also determined. Using the methods of molecular mechanics, the energy contributions of intramolecular interactions in low-energy conformational states of the molecule were obtained. Based on quantum-chemical calculations, the distribution of electron density and the values of dipole moments of the most optimal spatial structures of the YSL tripeptide molecule were determined. The reactivity of the tripeptide was also studied by quantum chemical calculations based on the obtained electronic characteristics of each low-energy conformation of the molecule. Using the calculated coordinates of the atoms of the energetically preferable structures of the molecule, their molecular models were built, the comparison of which makes it possible to identify the structural criteria necessary to create a drug suitable for clinical use.

Exploring the Mn doped BaTe alloy for spintronics and energy harvesting applications

In the present study, the ferromagnetic semiconductor behavior of Mn doped BaTe is reported along with their physical properties. The calculations are done by full potential linearized augmented plane wave (FP-LAPW) approach within spin-polarized density functional theory (SP-DFT). Formation energies were computed to satisfy the stability of reported alloys. The spin-polarization is included in the calculations to study the electronic (band structure (BS), density of states (DOS)) and magnetic characteristics. Ba1−xMnxTe elucidates the magnetic semiconductor nature with direct band gap (Eg) in both spin channels while indirect Eg (1.66 eV) is observed for pure BaTe compound. Stable ferromagnetic (FM) states are vindicated owing to the p-d hybridization which are contributors in inducing magnetic moments (μ B) at interstitial and non-magnetic sites. The optical parameters (reflectivity, absorption coefficient, refraction, optical conductivity and dielectric function) were computed within an energy range of 0–10 eV. Thermoelectric (TE) features are also figured using Boltaz-Trap code in terms of thermal and electrical conductivity, figure of merit, Seebeck coefficient and power factor. The analysis of optical parameters suggests that the considered alloys is active within visible to UV-range, having potential applications in optoelectronic, photovoltaic and thermoelectric applications.

Structural, optoelectronic, and magnetic behaviors of Li2BeTM( TM= V, Cr, Mn, Fe)Se4 compounds using DFT investigations

Abstract In this work, we provide computational investigations of the electronic, the optical and the magnetic properties of the Li2BeTMSe4(TM = V, Cr, Mn, Fe) compounds using the first-principle calculations based on the density functional theory. In this respect, we employ the generalized gradient approximation corrected by the Tran-Balaha modified Becke-Johnson exchange potential to obtain more accurate results. Among these outcomes, we first examine the electronic properties such as the band energy dispersion and the state densities. Regarding this, the Li2BeTMSe4 quaternary family is found to have an indirect band gap of 1.910 eV, 1.905 eV, 2.223 eV and 1.278 eV for TM= V, Cr, Mn, and Fe, respectively. Further, an examination of the optical properties reveals that the computed optical absorption spectra cover a broad energy range in the visible and the ultraviolet spectrum. Motivated by spintronic applications, we additionally determine the total and the local magnetic moments. Then, we compute the associated Curie temperature via a linear relation with the total magnetic moments. Among others, the Li2BeTMSe4(TM= V, Cr, Mn, Fe) materials involve acceptable temperatures showing potential applications for high temperature nano-devices activities. Comparing the obtained findings with the available ones, the acquired results indicate that the Li2BeTMSe4(TM = V, Cr, Mn, Fe) materials exhibit a wide range of applications in solar cells, optoelectronics, and other fields.&amp;#xD;

Measurement of the neutron total cross section of 9Be at the Back-n white neutron source of CSNS

Abstract The neutron total cross section data of 9Be play an important role in nuclear structure model research of light nuclei and nuclear power installations. A measurement of the neutron total cross section of 9Be in the 0.3 eV-120 MeV energy region has been carried out by using time-of-flight method and transmission method with the Neutron Total Cross Sectional Spectrometer (NTOX) based on the multi-cell fast fission chamber at the China Spallation Neutron Source (CSNS)- Back-n white neutron source (Back-n). The fission count-neutron energy distributions of 235U and 238U without sample and with Be samples in three thicknesses were measured in the double-bunch operation mode during beam power of 100 kW. The Bayesian method is used to eliminate the influence of the double-bunch problem on neutron measurement in the energy region above 10 keV. The neutron total cross section of 9Be results is well consistent with ENDF/B-VIII.0 evaluation library data in 0.3 eV-20 MeV energy region. In the energy range of 0.3 eV to 10 keV, the deviation between our results and the evaluation results of ENDF/B-VIII.0 is within 2.5%, which is within 15% from 0.01-20 MeV. In the resonance energy region, the measured resonance energies in our experiment are 0.63 MeV, 0.82 MeV and 2.8 MeV respectively. The results show that the total cross section uncertainties of three thicknesses Be samples are within 2.2% in the energy region below 1 MeV. The total cross section uncertainty of 30 mm Be from 235U is the smallest and less than 5% in the energy region 0.3 eV-120 MeV. The results of this experiment can provide technical support for further data analysis and related nuclear data evaluation.

Study of 113In(α, α) elastic scattering to determine α-optical potential relevant for astrophysical γ-process

Abstract The α-optical potential is one of the key input parameters used to measure the reaction rate of the (γ, α)-process using the Hauser-Feshbach statistical model and the principle of detailed balance. α-elastic scattering experiment on 113In p-nucleus was carried out in the energy range E lab = 26−32 MeV. The vacuum evaporation technique was used to prepare the 113In target (∼86 μg cm−2). An energy-dependent local optical potential parameters set was obtained by analysing the experimental elastic scattering angular distribution data. The local potential parameters are extrapolated for lower energies and are used to calculate the 113In(α, γ) reaction cross-section.

Two-photon absorption in quantum dots with Hellmann potential

Abstract We study the nonlinear optical absorption properties of a spherical quantum dot with Hellmann potential, focusing on the two-photon absorption (TPA) process, using GaAs/AlGaAs material as an example. { The radial Schr"{o}dinger equation is solved using the Nikiforov-Uvarov method, while the two-photon absorption coefficient is determined through second-order perturbation theory concerning the electron-photon interaction}. Our study shows that the intraband transition has a smaller energy transition than the interband transition, leading to TPA spectra for the intraband transition that is restricted within a smaller energy range and exhibits a higher peak value than those for the interband transition. The peak corresponding to $\ell=2$ consistently appears to the left of the peak corresponding to $\ell=1$ in both intraband and interband transition cases. Additionally, the dependence of the absorption peak position on the order of transition, $n$, differs between intra- and inter-band transitions. We also observe blue shift behavior in the TPA spectra as all three parameters, $r_0$, $V_{0e}$, and $\eta$, increase. Our investigation has the potential to enable the design of novel photonic devices, ultra-fast optical switches, and highly efficient solar cells through the optimization of quantum dot material properties.

Comprehensive theoretical investigation of NaAlX (X=C, Si and Ge) half-Heusler compounds: Unveiling the multifaceted properties for advanced applications

In this work, we have extensively investigated the characteristics of ternary half-Heusler (HH) materials, specifically NaAlX (X[Formula: see text][Formula: see text][Formula: see text]C, Si and Ge), employing ab-initio computations in density functional theory (DFT) framework. Various aspects, including stability parameters, electronic, optical and thermoelectric (TE) parameters have been examined. The computed lattice constants of NaAlX (X[Formula: see text][Formula: see text][Formula: see text]C, Si and Ge) were found to be, respectively, 5.398, 6.301 and 6.389[Formula: see text]Å which are in excellent agreement with the previously available data. The electronic band structures showed that the studied materials exhibit semiconducting behavior with a corresponding band gap of 1.961, 0.999 and 0.846[Formula: see text]eV, respectively. Specifically, NaAlC and NaAlGe compounds were found to have a direct energy band gap at the [Formula: see text]-point, while NaAlSi displayed an indirect band gap at the [Formula: see text]–X point. Elastic and thermodynamic parameters were examined, confirming that the titled compounds possess mechanical, dynamic and thermal stability. Additionally, the optical response of the materials has been analyzed within an energy range of 0–13[Formula: see text]eV. The TE parameters exhibited maximum ZT values of 0.998, 0.992 and 0.990 for NaAlX (X[Formula: see text][Formula: see text][Formula: see text]C, Si and Ge) materials, respectively, at 300[Formula: see text]K, suggesting promising TE performance at room temperature.

Assessment of radiation shielding capability of a high-density TeO2–Tl2O–Ag2O glass system: A simulation and theoretical studies

We investigated the shielding properties of four selected glass samples among the 66 samples. These glass samples had the following compositions and densities: S1 (55TeO2+45Ag2O, density 6.28 g/cm3), S2 (55TeO2+5Tl2O+40Ag2O, density 6.37 g/cm3), S3 (50TeO2+15Tl2O+35Ag2O, density 6.49 g/cm3), and S4 (40TeO2+55Tl2O+35Ag2O, density 7.20 g/cm3). These glasses exhibit high density. We compute the mass attenuation and linear attenuation coefficients for these samples using MCNPX simulations and Phy-X software between 0.001 MeV and 15 MeV energy range. The derived mass attenuation coefficient (MAC) enables the calculation of key radiation shielding metrics. The tenth value layer, the half value layer (HVL), the mean free path (MFP), and the effective atomic number (Zeff) were also determined. Values of LAC values for S1, S2, S3 and S4 glasses span 244.91 to 0.24932 cm⁻1, 319.52 to 0.2625 cm⁻1, 447.24 to 0.28491 cm⁻1 and 379.480 to 0.273 cm−1, respectively. Correspondingly, HVL values range from 0.0028 to 2.78005 cm, 0.0021–2.6403 cm, and 0.00154–2.4327 cm and 0.002135–2.917403 cm for S1, S2, S3 and S4 glasses, respectively. Our findings reveal that results from both MCNPX and Phy-X exhibit consistency, supported by computed relative differences. Notably, the glass sample with a relatively higher TlO2 concentration demonstrates superior shielding properties across the entire energy spectrum. Importantly, these glass samples can significantly lower the strength of the x-rays and γ-rays.

Properties of the chalcogenide-based double perovskites Ba2NbBiS6 and Ba2TaSbS6 with respect to structural, electronic and optical aspects

In this work, we delve into the investigation of the structural, electronic, and optical properties of Ba2NbBiS6 and Ba2TaSbS6 chalcogenide-based double perovskites, which are structured in the cubic space group [Formula: see text] form. We have performed first-principles calculations using density functional theory (DFT) to study the above properties. The electronic band structure and density of states of this compound have been investigated, and their results show that Ba2NbBiS6 and Ba2TaSbS6 exhibit a semiconducting nature with an indirect energy gap of 1.680[Formula: see text]eV and 1.529[Formula: see text]eV, respectively. Furthermore, an investigation was conducted on the optical properties of the compounds throughout the energy range spanning from 0[Formula: see text]eV to 55[Formula: see text]eV. This investigation focused on many parameters, including dielectric functions, optical reflectivity, refractive index, extinction coefficient, optical conductivity, and electron energy loss. The optical data obtained from the calculations reveals that all compounds demonstrate isotropy in optical polarization. Furthermore, it has been noted that our compounds exhibit absorption properties inside the ultraviolet (UV) region. Consequently, these materials hold promise as potential candidates for various applications, such as UV photodetectors, UV light emitters, and power electronics. This is primarily attributed to their inherent absorption limits and the presence of prominent absorption peaks in this spectral range. In brief, chemical mutation techniques have been employed to manipulate the characteristics of double-sulfide perovskites to develop durable and environmentally friendly perovskite materials suitable for solar purposes.

Improving instrumental neutron activation analysis detection limit using Monte Carlo simulation for lanthanides determination in Algerian phosphate

ABSTRACT Instrumental Neutron Activation Analysis (INAA) is one of the best methods to analyse Rare Earth Elements (REE) with a low detection limit in phosphate samples. Since most lanthanides emit gamma rays at the energy below 1000 keV, this energy range is affected by the Bremsstrahlung noise of beta emission produced by the 31P(n,γ)32P reaction, when the irradiation of the P2O5 composing the phosphate matrix (approximately 30%). This beta (β−) spectrum with a maximum energy of 1.71 MeV (average energy of 695 keV) affects the gamma spectrum and will reduce the detection limit significantly, other factors decrease the detection limit of lanthanides like neutron self-shielding and interference. In the present work, an analysis methodology based on optimising the measurement parameters of the INAA technique was implemented to improve the detection limits for the precise evaluation of lanthanide concentrations in Algerian phosphate deposits. The complete procedure was developed using a combination of a Monte Carlo simulation approach and experimental measurements. Two models were developed based on Monte Carlo simulation for the calibration of HPGe detector efficiency and the optimisation of type and filter thickness to reduce the beta spectrum (Bremsstrahlung) emitted by the 32P produced by neutron capture reaction 31P(n, γ) 32P. The developed model allowed a considerable improvement in the detection limit of the INAA technique and reduced the uncertainty in the lanthanide concentration. Finally, the methodology was applied to determine lanthanide elements in phosphate samples with good precision.