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Brucellosis infection could be eradicated by using an effective vaccine. InfC gene expression generates one of the main Brucellapathogenesis proteins. The purpose of this study was to design a new vaccine against Brucelladisease by in silicodetermination of epitopes of infC protein.

The in-plane hybrid structure of hexagonal boron nitride (BN) and graphene (Gr) with carbon–boron and carbon–nitrogen interfaces under different boron-nitride and graphene concentrations for hydrogen storage properties is summarized in detail. The stability of these structures is verified from the cohesive energy and molecular dynamics calculations. The electronic band gap of the pristine hybrid structures is reduced with an increase in the graphene concentration. The structural properties such as bond length and bond angle are preserved for both graphene and boron nitride in the hybrid system. The pristine C–B-terminated system has an average adsorption energy of −0.046 to −0.076 eV/H2in the field-free condition upon dual site hydrogen molecules insertion with a theoretical hydrogen storage capacity of 10.18–10.38 wt %. In the presence of an external electric field, the adsorption energy of the hydrogen molecules linearly increases due to the polarization of the adsorbed hydrogen molecules. From our study, we report a threshold external electric field strength of ≥1.6 V/Å to achieve the lower bound criteria of average adsorption energy set by the United States Department of Energy (US-DOE) for a C–B-terminated structure and higher threshold EF for the C–N-terminated structure. While in the presence of the electric field, the average adsorption energy goes beyond −0.20 eV/H2with the hydrogen storage capacity of 10.18–10.38 wt % upon dual site hydrogen molecules adsorption on in-plane nBN-mGr (n= 5, 4, 3, 2, 1 and m= 1, 2, 3, 4, 5).

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Spinel chalcogenides have great potential for optoelectronic and thermoelectric applications and therefore received huge attention in recent years. In this regard, here we investigate the structural, optical, electronic, and thermoelectric characteristics of HgY2S4and HgY2Se4spinel chalcogens using a density functional theory-based WIEN2k package. Ground state optimization of crystal structure and thermodynamic stability of the material is probed from the energy volume optimization graph and computation of enthalpy of formation. The computation of Poisson's and Pugh's ratios revealed the ductile nature of these materials. Bandgap calculation is performed using TB-mBJ package, which exposed the direct band nature of these semiconducting materials with bandgap values of 1.2 eV for HgY2S4and 0.6 eV for HgY2Se4. The evaluation of optical characteristics and transport features revealed these compositions’ potential for optoelectronic and thermoelectric applications.

Triple cation mixed halide perovskite solar cells have exhibited a great deal of interest and could be the potential candidate with an enhanced power conversion efficiency (PCE) as compared to conventional perovskite solar cells. In this article, we have simulated the various photovoltaic characteristics of [Cs0.05(MA0.17FA0.83)0.95Pb(I0.83Br0.17)3] based mixed cation mixed halide perovskite solar cells in n-i-p configurations. We have demonstrated and substantiated the experimentally reported device performances in identical device configurations using the same materials. The effect of variation in different hole transport layers, electron transport layers, doping density, and the thickness of various layers on device performance is thoroughly analyzed through our simulation. Further optimization of device performance is carried out by changing the thickness, doping concentration, and defect density of the active layer, and the PCE of 25.95% is achieved.

Double perovskite (DP) halides are a reliable source of renewable energy that plays a vital role to fulfill the requirements of energy crunch. Therefore, the analysis of these perovskite halides have promising uses for thermoelectric and optoelectronics purposes. We investigated the thermoelectric and optoelectronics properties of Rb2KScI6and Cs2KScI6halides for use in renewable energy devices by using FP-LAPW + lo approach based on DFT. The calculated Goldsmith's tolerance factor and enthalpy of the formation of studied halides reveal that these are structurally and thermodynamically stable in cubic phase. Moreover, the analyzed value of Poisson and Pugh ratio reveals ductile nature of these materials. Further, we computed the bandgaps by analyzing electronic characteristics. For bandgap calculations of Rb2KScI6(Eg = 2.75 eV) and Cs2KScI6(Eg = 2.65 eV), we employed mBJ potentials to obtain precise values as comparison to experimental values. The complex dielectric function used to reveal the optical properties of the analyzed materials. The calculated optical results clearly show the maximum absorption of light in infrared (IR) region revealed that the analyzed materials are appropriate for optoelectronic purposes. The thermoelectric behavior was examined as to figure of merit (ZT), electrical-conductivity (EC), the Seebeck-coefficient (S) as well as thermal-conductivity. Animatedly in future, the analyzed consequences would be supportive to experimental investigation of Rb2KScI6and Cs2KScI6for renewable energy device applications.

•Both compounds are optimized in stable ferromagnetic phase.•PBE-GGA and GGA+U are used to compute the band structures and density of state.•Spin orientations declare full metallic character in ThCo2X2compound.•High magnetic moment for ThCo2Ge2affirms strong ferromagnetism than ThCo2Si2.

A series of cobalt ferrite nanoparticles were prepared using hydrothermal process by varying the reaction temperature. The structural, magnetic and dielectric properties have been studied with the help of X-ray diffractometer (XRD), vibrating sample magnetometer (VSM) and impedance analyzer respectively. XRD spectra of all samples confirmed the formation of cobalt ferrite (CoFe2O4) nanoparticles (NPs). The lattice constant ‘a’ for temperature series samples is averaged around 8.4023 Å. Crystallite size of temperature series is calculated by Debye–Scherer formula that lies in the range of 15.04–20.49 nm. Its values increase because the chance of coalescence increases by increasing temperature. The maximum packing factor is obtained for the sample with highest reaction temperature. From VSM data, we get the M–Hhysteresis curves for complete temperature series which confirms the magnetic nature. The maximum saturation magnetization 150.67 emu/g is obtained for the sample prepared at highest temperature. Different magnetic parameter such as saturation magnetization, coercivity, retentivity, squareness ratio, anisotropy constant and magneton number has been calculated from VSM data. AC response of all prepared ferrites was studied with impedance analyzer of frequency range 20 Hz to 20 MHz. Ferrites are the insulating materials, so, eddy current does not induce in transformer cores made of ferrite materials. In the medical field cobalt ferrite is used for drug delivery, as a biosensor and in MRI.

In present study, the effect of pressure on the electronic, thermoelectric and optical properties of cubic KNbO3compound is investigated using Predew-Burke-Ernzerhofgeneralized gradient approximation (PBE + GGA) in the framework of density functional theory. At 0 GPa, the calculated electronic band structure and density of states predict the indirect semiconducting nature of KNbO3, which is transformed into direct band gap at 180 GPa. Furthermore, the band gap decreases from 2.3 eV to 2 eV as the pressure upsurge from 0 GPa to 180 GPa. For optical characteristics, absorption and extinction coefficients, dielectric function, reflectivity, refractive index, and optical conductivity are calculated in the range of 0–10 eV at different pressures. Moreover, thermoelectric (TE) properties of the mention compound are investigated in terms of electrical conductivity, power factor, Seebeck coefficient, thermal conductivity using the Boltz-Trap code. The Seebeck coefficient decreases and electrical conductivity increases with the increase in pressure. Hence, KNbO3is found to be a suitable compound for optoelectronic and thermoelectric applications.

Sol-gel procedure was taken into consideration to produce ferrite series with chemical formula MnYbyFe2-yO4with y = 0.00 to 0.10 (step = 0.025). Structural, electrical and magnetic aspects of ytterbium (Yb) switched Mn-ferrites were the main focus. Every sample exhibited cubic phase spinel assembly. Exchange of ytterbium with iron in the system produced enlargement in coercivity while abridgment in remanence and saturation magnetization. Involvement of Yb ion in the ferrite assembly led to reduction of both real and imaginary constituents of permittivity. The ytterbium introduction in the lattice enhanced the value of impedance. The examination of hysteresis loop was done under the range of -2K to +2KOe. Temperature dependent resistivity, activation energy and drift mobility were carried out by two probe method. The characterization outcomes recommended that the compounds are appropriate for microwave absorption usages.

This article presents the variation of structural, electronic, thermal and optical properties of a halide perovskite CsYbBr3with increasing pressure, employing density functional theory. The pressure effect was determined in range of 0–15 GPa. In which stability of CsYbBr3remains valid, as, verified from negative values of enthalpy of formation and phonon dispersion curves. A significant change was observed in lattice constant, bond lengths, bulk modulus and its pressure derivative, volume and ground state energy, with increasing pressure. The calculated electronic properties presented CsYbBr3as a semiconductor with direct band gap of 3.61 eV. However, pressure rise shift the Yb-dstates toward the Fermi level and causes a decrease in band gap. At 12 GPa, CsYbBr3presents the semi metallic nature while further increase in pressure makes it as metallic. Moreover, Debye temperature (Grüneisen parameter) was observed to increase (decrease) with pressure rise while the lattice thermal conductivity was found to increase. The calculated optical properties exposed the suitability of CsYbBr3in pressure tunable opto-electronic devices.

Hybrid organic–inorganic perovskite solar cells (HOIPs), especially CH3NH3PbI3(MAPbI3), have received tremendous attention due to their excellent power conversion efficiency (25.2%). However, two fundamental hurdles, long-term stability and lead (Pb) toxicity, prevent HOIPs from practical applications in the solar industry. To overcome these issues, compositional engineering has been used to modify cations at A- and B-sites and anions at the X-site in the general form ABX3. In this work, we used the density functional theory (DFT) to incorporate Rb, Cs, and FA at the A-site to minimize the volatile nature of MA, while the highly stable Ca2+and Sr2+were mixed with the less stable Ge2+and Sn2+at the B-site to obtain a Pb-free perovskite. To further enhance the stability, we mixed the X-site anions (I/Br). Through this approach, we introduced 20 new perovskite species to the lead-free perovskite family and 7 to the lead-containing perovskite family. The molecular dynamic (MD) simulations, enthalpy formation, and tolerance and octahedral factor study confirm that all of the perovskite alloys we introduced here are as stable as pristine MAPbI3. All Pb-free perovskites have suitable and direct band gaps (1.42–1.77 eV) at the Γ-point, which are highly desirable for solar cell applications. Most of our Pb-free perovskites have smaller effective masses and exciton binding energies. Finally, we show that the introduced perovskites have high absorption coefficients (105cm–1) and strong absorption efficiencies (above 90%) in a wide spectral range (300–1200 nm), reinforcing their significant potential applications. This study provides a new way of searching for stable lead-free perovskites for sustainable and green energy applications.

The solar cells and thermoelectric generators are the main sources of renewable energy. In current article, we have analyzed the electronic, optical, and transport characteristics of K2TiI6and Rb2TiI6by density functional theory (DFT) based Wien2k code through modified Becke and Johnson (mBJ) potential. The structural and thermodynamic stability are certified by tolerance factor (0.99–1.0) and negative formation energy. The bonding nature is illustrated by color charge density. The band gap of 1.39eV and 1.48eV for K2TiI6and Rb2TiI6demonstrate the maximum absorption of light takes place in visible region (1.5eV–3eV), which makes them new potential materials for solar cells. Moreover, the reflection of light and optical loss is negligible in the visible region. The transport characteristics have been explained by classical Boltzman transport (CBT) based BoltzTraP code in terms of thermal to electrical conductivity ratio, Seebeck coefficient, and figure of merit. The figure of merit lies between 0.75 to 0.76, which is decent for thermoelectric characteristics.

Full potential linearized augmented plan wave (FP-LAPW) method based on density functional theory (DFT) is employed to investigate the structural, optoelectronic, elastic and magnetic properties of cubic XAlO3(X = Nd, Gd) perovskites. The optimized unit cells have been used to expose the thermodynamic stability in the ferromagnetic ground state, which is further verified in terms of enthalpy of formation (ΔHf) and cohesive energy. The spin polarized band structure and density of states illustrate that NdAlO3perovskite has a half metallic character, and GdAlO3has a semiconductor nature. The bulk modulus, elastic constants, Poisson's ratio, shear modulus, anisotropy and Young's modulus are also determined. The calculated magnetic moments of cubic NdAlO3and GdAlO3are 3 μB and 7 μB, respectively and the magnetization is largely originated from Nd and Gd atoms. Furthermore, the optical parameters like reflectivity, optical conductivity, dielectric constants, absorption coefficient and refractive index are also investigated. The results suggest that these compounds could be promising materials for spintronic and optoelectronic devices.

Cerium oxide (CeO2) nanoparticles (NPs) were mixed with titanium dioxide (TiO2) in different wt.% to obtain an improved composite photoanode with better electron-injection property. Using these composite photoanode materials, dye-sensitized solar cells were fabricated, and photovoltaic performances were evaluated. For performance comparison, a cell with pure TiO2 as a photoanode was also prepared. Devices fabricated using composite photoanodes with 1%, 3%, 5%, and 7% of CeO2 showed power conversion efficiency (PCE) of 7.0%, 5.68%, 5.64%, and 3.97%, respectively. Whereas, the cell with pure TiO2 as photoanode showed an efficiency of 3.35%. This enhanced PCE was attributed to the presence of CeO2 within the photoanode, which helps to reduce the charge recombination loss and improve photo-absorption. Eventually improved the open-circuit voltage and short-circuit current. Pure and composite photoanode samples were characterized for their optical and morphological properties. Homogeneous distribution of CeO2 NPs within the composites were confirmed by TEM analysis.

The bandgap was tuned to investigate the electronic and optical aspects using first-principle calculations for solar cells and other optical applications. The bandgap range varies from 1.6 to 2.1 eV for Ga1−xAlxAs and from 0.8 to 1.5 eV for Ga1−xAlxSb (x= 0.0, 0.25, 0.5, 0.75, 1.0). The dispersion, polarisation, and attenuation have been illustrated in terms of transparency and maximum absorption of light. The inversion of polarised atomic planes near the resonance allows the maximum absorption in ultraviolet to visible region. The Penn’s model (ε1(0) ≈ 1 + (ℏωp/Eg)2) and optical relation ε1(0)${\varepsilon_{1}}\left(0\right)$= n2(0) confirm the reliability of our finding. The maximum absorption, optical conduction, and minimum optical energy loss increase the credibility of the studied materials for energy storage device manufacture.

Spintronic technology and energy applications benefit greatly from the exceptional characteristics of rare-earth-based spinel chalcogenides. Examining the electrical, magnetic and thermoelectric properties of HgNd2Z4(Z = S, Se) in a systematic manner is essential for the strategic advancement of spin polarized current in a spintronic device. In this recent study, the WIEN2K code was employed to comprehensively analyze these properties. The calculated lattice constants, obtained using the generalized gradient approximation (GGAsol-PBE), closely match experimental findings of the similar family compounds. The examination of the stability of ferromagnetic states in the ground state involves comparing energies between anti-ferromagnetic and ferromagnetic states. Moreover, an assessment of the stability of the cubic phase in both spinels was conducted using analyses of the phonon dispersion curve, formation energy and Born stability criteria. The ductility characteristics were examined through the calculation of Poisson's and Pugh's ratios. Furthermore, details regarding the density of states, spin polarization, exchange coupling and Curie temperature were provided to explore the characteristics associated with ferromagnetism. Potential optoelectronic applications were proposed, leveraging the direct band gaps of 1.4 and 1.0 eV for HgNd2Z4(Z = S, Se) respectively, within the visible spectrum. Particularly noteworthy is the effective light absorption of HgNd2Se4in the visible range, characterized by prominent peaks that facilitate the transition of electrons from the valence band (VB) to the conduction band (CB). Additionally, the study extends to thermoelectric characteristics, determining various factors such as Seebeck coefficient (S), figure of merit (ZT), electrical and thermal conductivities of the evaluated spinels.

First-principles calculations of the second-order optical response functions and the dielectric functions of urea [CO(NH2)2] and some of its derivatives such as monomethylurea (H2NCONHCH3, MMU), and N,N′-dimethylurea (H3CHNCONHCH3, DMU) crystals are performed. On the basis of the density functional theory (DFT) in the local-density approximation (LDA), the highly accurate full-potential projected augmented wave (FP-PAW) method was used to obtain the electronic structure. Over a wide frequency range (0.0–10.0 eV), the dielectric constants and second-harmonic generation (SHG) susceptibilities of the urea crystal family have been obtained, and the results are in good agreement with the experimental values. The origin of the linear and nonlinear optical (NLO) properties of the urea crystal family has been analyzed by coupling the calculated electronic structure and optical spectrum. The prominent spectra of χ(2)are successfully correlated with the dielectric function ε(ω) in terms of single-photon and double-photon resonances. The virtual electron (VE) and virtual hole (VH) processes have also been performed for the urea crystal family. From the research into the electron deformation density, crystal configuration, substitutional group, and so forth, it is found that the origin of the SHG of the urea crystal family is the charge transfer due to the strong “̀push–pull” effect along the hydrogen bond, which favors a head-to-tail arrangement of the molecules and enhances the SHG response. The electron-donating substitutional group supplies more electrons to the electron-accepting group, and helps to form large dipoles in molecules. The influence on the NLO properties of the local symmetry of the substitutional group is also discussed in detail.

This paper investigates the properties of cubic halides KCrX3(X = Cl, Br, I) compounds focusing on their half-metallic (HM) ferromagnetic and thermoelectric characteristics. The analysis is performed using the Wien2k and BoltzTrap coding. The stability of our compounds in the ferromagnetic (FM) phase is established by the higher energy release compared to the antiferromagnetic (AFM) phase. The calculated value of Poisson ratio and Pugh ratio greater than their cutoff limit (0.26 and 1.75) reveal that our examined materials are ductile in nature. To examine the electronic structure, the Trans-Bhala modified Becke Johnson potential (TB- mBJ) is employed to investigate half-metallic nature. The density of states (DDS) analysis indicates significant contributions from X-p states in the valence band and Cr 3d-states in the conduction band. A comparative analysis of crystal field (ΔEcrystal) and exchange (indirect Δx(Pd) and direct Δx(d)) energies provides insights into the primary role of electronic spin in the ferromagnetic behavior. The observed value (4 μB) of total magnetic moment of the investigated halide perovskites suggest that they could be promising candidates for spintronic materials. Lastly, we compute the thermoelectric parameters within a temperature range of 200 K to 800 K to explore the potential application in renewable energy devices.

Improving the performance of thermoelectric materials for clean energy production via structural manipulation is considered as an effective route to advanced thermoelectrics. Here, we report the improved thermoelectric response of single-layered GeS (α-GeS) by developing its two new polymorphs, namely, γ-GeS and ε-GeS. The two new polymorphs exhibited flat-band gap edges, which resulted in large Seebeck coefficients (thermopowers) due to the large density of states around the Fermi level. The favorable combination of large thermopowers and considerable electrical conductivities resulted in large values of thermoelectric power factors (PFs) and thermoelectric figure of merit (ZT). The room-temperature ZT values of γ-GeS and ε-GeS exceeded a benchmark value of unity and approached as large as 1.67 (for γ-GeS at 500 K) and 1.07 (for ε-GeS at 1000 K). These monolayers demonstrated large PFs corresponding to band gap edges that can be enhanced by low-level p-type doping. Moreover, their optimal PFs go through further enhancement with increase in temperature. The investigations of energetic stability revealed high thermodynamic stability of these monolayers, which suggest the feasibility of their experimental growth. These investigations were performed through the density functional theory and Boltzmann transport theory-based computational approaches. Our study suggests structural manipulation as an effective tool for improvement of the thermoelectric response of IV monochalcogenides for high-efficiency thermoelectric applications.

•AB3(A = Si, Ge, Sn and B = Cr, V, Nb) compounds were studied by FP-LAPW method.•The calculated lattice constants are found to be consistent with experiment.•Band structures reveal the metallic nature of these compounds.•The compounds are anisotropic, ductile and resistant to plastic deformation.•Linear optical properties were studied comprehensively.

•The electronic, magnetic and mechanical properties under pressure are reported.•The phase transition under pressure is addressed.•RbVF3is a novel inorganic perovskite type spin gapless semiconductor.•The mechanical properties have been considered.

Ceramic photocatalysts have become a focus of several research works in the sonochemistry community owing to their potential for enhancing the degradation of organic pollutants during sonocatalysis or sonophotocatalysis. Although various ceramic materials have been developed and employed in hybrid advanced oxidation processes in the past decades, the physics and chemistry governing the photocatalytic performance of these materials at the atomistic level are usually derived from assumptions based on experimental observations. In the present study, we employ computationally economical density functional theory (DFT)-based ab initio calculations for evaluating the physical properties of undoped and doped modifications of large-band-gap ceramics. Motivated by a recent experimental work, we have studied the thermodynamic and optoelectronic properties of pristine- and Ce4+-doped BaZrO3compounds for selected concentrations of cerium dopant (x= 0, 0.037, and 0.125). Our results provide a clear insight into the relationship between dopant concentration xand the improved optical properties of BaZr1–xCexO3compounds, which is directly related to the enhancement of their photocatalytic activity. The physical properties of Ce4+-doped BaZrO3ceramics obtained using DFT calculations are not only found to be in good agreement with experiment, but can also provide a deeper understanding of their tunable optoelectronic properties, which can be tailored to attain functionalities required for practical applications. Based on our results, we conclude that modern DFT can serve as an efficient tool for predicting ceramic photocatalysts suitable for advancing hybrid advanced oxidation processes of sonochemistry.

This research contribution investigates a way of improving performance of CIGSe‐based second‐generation thin‐film solar cells by analyzing output parameters of two reference cells using cadmium sulfide and zinc sulfide as buffer layers. The performances are improved by acknowledging both the exceptional properties of ZnS as a buffer layer, and the beneficial contributions of an indium‐enrich layer, which form a surface defect layer at the ZnS/CIGSe heterojunction. SCAPS‐1D numerical modeling software is used to conduct calculations, and the structure using ZnS enables achieving an efficiency of 24.31%. Deeper investigation on the effects of variation of functional layers properties such as bandgap, electron affinity, doping level, and thickness enables retaining an optimized structure, and results show an improved efficiency of 25.22% and a fill factor of 80.26%, indicating of a fluid flow of charge carriers, thus a more stable device. All simulations are performed considering experimental environment parameters, an external temperature of 300 K, light illumination of AM1.5G, and defects states are assumed in both the bulk and at interfaces. High‐performance thin‐film CIGS solar cells are achieved by considering the remarkable properties of ZnS as a buffer layer, and the benefits of an indium‐enrich layer form at the ZnS/CIGS heterojunction. Optimization of bandgap, electron affinity, thickness, and doping enable to obtain efficiency and fill factor of 25.22% and 80.26%, respectively.

The structural, electronic, optical and thermoelectric properties of ternary CaBe2X2(X = N, P, As, Sb and Bi) have been investigated comprehensively for the first time using density functional theory. All the compounds are optimized to obtain their ground states. Computed structural parameters agree to the available experimental results. Electronic band structure calculations reveal the semiconducting nature of the compounds, while bang gap decreases by changing the anion X from N to Bi the band gap decreases. In the valence band, major contribution is due to X-pstate, while in conduction band (CB) the major contribution is mainly due to the Ca-dstate. Furthermore, electron charge density plots reveal ionic bonding character with small covalent bonding. Optical properties are calculated in detail. Static value of refractive index shows inverse variation with band gap. The refractive indices of these compounds are high in the infrared region and gradually decreased in the visible and ultraviolet region. The thermoelectric properties are studied using Boltzmann statistics through BoltzTraP code. High optical conductivity peaks and figure of merits (ZT) for compounds reveal that they are good candidates for the optoelectronics and thermo-electric devices.

In the chalcopyrite (or tetragonal) phase, different physical properties of the ternary LiMX2(M = Al, Ga, In and X = S, Se, Te) compounds are studied by the very accurate density functional method. The optimized lattice constants and the bandgaps are close to the existing experimental data. In addition, for most of the LiMX2compounds, when the cations change from Al to In and anions from S to Te, the lattice constant and equilibrium volume for the crystal unit cell increase whereas the bulk modulus decreases. Using different generalized gradient approximations, the band structure calculations are performed. Generally, it was observed that there exists a decreasing tendency of the bandgap energies except for the LiAlSe2, LiInSe2, and LiGaTe2compounds due to the change from Al to In as well as the change from S to Te. The bonding analysis shows that ionic bonds are present between the Li-X atoms, while a covalent bond exists between the M cations and X anions. The optical properties of the compounds are studied by calculating the real and imaginary components of the refractive index, reflectivity, optical conductivity, and birefringence. In addition, the optical properties from the calculations show that these materials are appropriate applicants to be utilized as Bragg’s reflector or applied in optoelectronic and solar cell technology.

Pnictogen-based Zintl compounds have fascinating properties. Nowadays these compounds have gained exceptional interest in thermoelectric and optoelectronic fields. Therefore, in this work the structural, electronic and optical properties of SrZn2Pn2(Pn=N, P, As, Sb, Bi) compounds were studied using state-of-the-art density functional theory. The optimised lattice parameters (ɑ, c, c/ɑand bond lengths) are consistent with the experimental results. The bulk moduli and c/ashowed a decrease when changing the Pnictogen (Pn) anion from N to Bi in SrZn2Pn2(Pn=N, P, As, Sb, Bi). The modified Becke-Johnson potential is used for band structure calculations. All compounds show semiconducting behaviour except SrZn2Bi2, which is metallic. Pn-p, Zn-dand Sr-dplay an important role in defining the electronic structure of the compounds. The optical conductivity and absorption coefficient strength are high in visible and ultraviolet regions. These band structures and optical properties clearly show that SrZn2Pn2compounds are potential candidates in the fields of optoelectronic and photonic devices.

We will review the electronic, magnetic excitation, vibrational and optical properties of various spin states of LaCoO3 by employing local density approximation + Hubbard U (LDA+ U) technique with the state of the art of both pseudo-potential and full-potential linearized augmented plane-wave (FPLAPW) plus local orbital (lo) methodologies. In the recent calculations, a rotationally invariant formulation of local density approximation (LDA) + U approach was incorporated. In our previous work, we involved the correlation effects which provide prominent contribution for various spin species such as low spin (LS), intermediate spin (IS) and high spin (HS) configurations as well as their combined spin states. The ground spin configuration was revealed as a nonmagnetic insulating, while the Co ions hold a LS configuration. With a slightly augmented energy, the IS state was followed by a HS state at a notably bigger energy. Employing the LDA+ U electronic structure calculations, the orbital ordering is found in IS state which originates from the Jahn-Teller (JT) and on-site Coulomb interactions. Our previous results and the earlier susceptibility measuring data for IS excitations in the LS low magnetic configuration, drive to the deduction of nonmagnetic-paramagnetic transition in LaCoO3 giving a signature of the gradual population of IS Co3+ ionic states at 90 K. The first thermally excited spin-configuration took place from LS to LS (CoLS 3+ = 87.5%)-IS (CoIS 3+ = 12.5%) ordered configuration, which could be discriminated from IS state or LS-HS. Our recent theoretical findings reported a development of an orbital ordering in the mixed spin states namely, LS-IS, LS-HS, and HS-IS phases. The phonon dispersion spectrum of LS configuration at high symmetry directions in the Brillouin zone (BZ) and phonon density of states will be also presented. The frequencies of Raman and IR modes and the major features of these modes will be provided. The excited-states of several spin configurations of LaCoO3, like the x-ray absorption spectra, optical conductivity, reflectivity, and electron energy loss function will be also reviewed. The optical spectra calculations would be useful to examine the spin configuration of Co3+ ion. The local excitation of IS cobalt ions in the LS ground state was identified as the first configuration. The next following excitation was determined to stabilize the mixed IS and HS Co3+ metallic states. At low temperature, for O 2p-Co 3d states, the density of states designated a notable IS Co3+ ions comparatively to the experimental valence band spectra. Conversely, the HS state was identified as the most remarkable configuration at high temperature. The line shape of O 2s and Co 3d core level spectra are also reviewed in this chapter. Our previous results indicated good accordance with the previous available experimentally works. The alteration in the spectra of various spin configurations of LaCoO3 discerned a variation in the spin state as a function of the change of temperature between 90 and 500 K. [ABSTRACT FROM AUTHOR]

Bandgap evolution with composition variation of ABX3perovskites is explored, where A = MA, FA, Cs, Rb; B = Pb, Sn, Ge; and X = I, Br, Cl. To identify alternative lead‐free and stable perovskite‐absorbing compositions, all possible combinations of compositions are screened under constraints of structural stability and optimal bandgap values. The comparative analysis reveals Cs‐, Rb‐, and Ge‐based perovskite as an alternative to MAPbI3's toxicity and stability issues. The Cs‐, Rb‐, and Ge‐based perovskites are lead free and structurally stable, with the requisite optical cum electrical properties. The numerical simulation of the proposed Cs1−yRbyGe(BrxI1−x)3‐based device shows efficiency above the 22% mark. All aspects of the proposed device are identical to MAPbI3, except that the MAPbI3absorber is replaced with a Cs1−yRbyGe(BrxI1−x)3‐based absorber. The bandgap and stability with composition variation of ABX3perovskites (where A = Methylammonium, Formamidinium, Cs, Rb; B = Pb, Sn, Ge; X = I, Br, Cl) were assessed for identifying alternative lead‐free and stable perovskite with high efficiency. The comparative analysis reveals Cs‐, Rb‐, and Ge‐based Cs1−YRbYGe(BrxI1−x)3perovskites as lead free, alternatives to MAPbI3toxicity and stability.

We present a theoretical study of polaron properties associated to the optical phonon modes induced by pressure on the beryllium chalcogenides. The calculations are performed using abinitiopseudopotential approach based on the density functional perturbation theory combined with maximally–localized Wannier functions. Features such as phonon frequencies, dielectric constants, effective polar field, polaron effective mass, Fröhlich coupling constant, Debye temperature, deformation potential, polaron diffusion constant, and maximally–localized Wannier functions have been determined. Good agreement is found between our simulated results and available data. In another case, our calculated values are totally predictive. We show that the pressure dependence of those physico–chemical considerations on the electric polarization field is found to vary monotonously. These studies form the basis for further development of models to describe polaron transport in the monocrystalline phase of BeX (X = S, Se, and Te) compounds such as bulk crystals.

Current studies stipulate that the performance efficiency of photovoltaic cells can be increased by incorporating a tandem architecture into the device configuration. This work includes an assessment of the photovoltaic performance parameters and optimization of the cesium lead iodide (CsPbI3)–silicon (Si) tandem solar cells (TSC) by applying the SCAPS 1D tool. The two terminal (2‐T) monolithic TSC device configuration with a top CsPbI3perovskite solar cell (PSC) consisting of IGZO as the electron transport layer material (ETL) and CuSbS2as the hole transport layer material (HTL) and a bottom c‐Si solar cell exhibits a fill factor (FF) and power conversion efficiency (PCE) of 73.16% and 27.07%, respectively, by establishing the current matching condition, while in the four terminal (4‐T) stacked layer configuration, the device exhibits a PCE of 30.68%. The device acquires this high PCE after the optimization of the thickness, dopant density, and defect density of the perovskite light active material and Si. A two terminal (2‐T) monolithic tandem solar cell (TSC) with a top cesium lead iodide (CsPbI3) perovskite solar cell (PSC) and a bottom c‐Si solar cell exhibits a fill factor (FF) and power conversion efficiency (PCE) of 73.16% and 27.07%, respectively, while a four terminal (4‐T) TSC exhibits a PCE of 30.68% with SCAPS 1D as the modeling tool.

Half-metallic ferromagnetism, mechanical as well as thermoelectric properties for rare earth-based spinels MgHo2Z4(Z = S, Se) were investigated using density functional theory (DFT). Structural optimization was done with PBEsol-generalized gradient approximation (GGA) to calculate the lattice constant of both spinels comparable to experimental data. In addition, Born stability criteria and negative formation energy show that our studied spinels are also structurally and dynamically stable in the cubic phase. For ferromagnetic (FM) state stability, we also calculated the energy differences among FM, antiferromagnetic (AFM), and non-magnetic (NM) states. Additionally, Curie temperatures of ferromagnetic phases were also estimated. We used Trans-Blaha improved Becke-Johnson (TB-mBJ) potential functional for electronics as well as magnetic characteristics, which lead to the consistent explanation of half-metallic ferromagnetism, representing the whole band-occupancy in material with exact detail of density of states (DOS). The stable FM state was examined in spinels due to the exchange splitting of Ho cation consisting of p-d hybridizations compatible with the result achieved for electronics band structure and DOS. Further, spin magnetic moment was explained in terms of anion, cation, and sharing charge on studied spinels. In addition, the calculated thermoelectric properties clearly show that operation range of these systems may be utilized by future experimental works for identifying the potential applications of these systems.

We present the results of energetic and electronic properties of ZnSe using $spds^{*}$ tight-binding method derived to fit accurately first-principles calculations. The present $sp^{3}d^{5}s^{*}$ tight-binding model incorporates all five $d$ orbitals per Zn atom in the basis set to get better description for the structural properties of ZnSe than in the $sp^{3}s^{*}$ basis. In this study, we incorporate the local environment dependent on-site atomic energy levels. Although, it was fit only to a few high-symmetry bulk structures, the model can be successfully used to compute the energies and structures of a wide range of configurations. In this approximation, we check the validity of tight-binding parameters that give a more realistic results for bulk, surface, small clusters and point defects. The tight-binding parametrization reproduces well the experimental measurements and ab-initiocalculations, indicating that it describes faithfully the underlying physics of bonding in ZnSe.

We present a theoretical study of the spin state of LaCoO3using local density approximation + Hubbard $U$ (LDA+$U$) approach based on pseudopotential method. The correlation effects play a significant role in the case of low spin (LS), intermediate spin (IS) and high spin (HS) configurations. The ground state is found to be a nonmagnetic insulator with Co ions in a LS state. Somewhat higher in energy, we find an IS state followed by a HS state at significantly higher energy. The orbital ordering in IS state driven by the Jahn--Teller (JT) and on-site Coulomb interactions is demonstrated based on the LDA+$U$ electronic structures. The phonon dispersion curve of the paramagnetic LS ground state at high symmetry directions of the Brillouin zone (BZ) and phonon density of states are also calculated. The frequencies of the Raman and IR modes are calculated and the main characteristics of these modes are discussed. The computed zone center phonon frequencies of LS state agree fairly well with the experimental results.

We study the magnetic properties of monoatomic Fe, Co, and Ni nanowires on wurtzite boron nitride (w-BN)(0001) using state-of-the-art first-principles calculations. Our results show that the most stable phase is the ferromagnetic Co(Fe) metal-atom chain adsorbed on the w-BN(0001) surface terminated by N layers. The monoatomic Co and Ni chains on the w-BN (0001) surface terminated by N layers are found to be excellent half-metallic ferromagnets with large half-metallic gaps (up to 0.65 eV). The monoatomic Co and Fe nanowires on B-terminated w-BN (0001) and Fe nanowires on N-terminated w-BN (0001) present large but not complete spin polarization. We found that the large magnetic anisotropy energy (MAE) of ferromagnetic atoms is caused by a magnetic Coulomb interaction between the ferromagnetic atoms and N and B atoms. In this case, the large spin−orbit coupling of the ferromagnetic atoms and the hybridization between the ferromagnetic atoms d-, N p-, and B p-like states are crucial. The w-BN (0001) surface acts as a simple structural template with the transition metal (TM) (Fe, Co, and Ni) chains for the formation of an artificial one-dimensional system. We demonstrate that the magnetic properties of TM atomic chains on the w-BN(0001) surface are responsible for different couplings with the substrate which are significant for future experiment investigations.

Over the past few years, metal halide perovskite solar cells have made significant advances. Currently, the single-junction perovskite solar cells reach a conversion efficiency of 25.7%. Perovskite solar cells with a wide band gap can also be used as top absorber layers in multi-junction tandem solar cells. We examined the dynamical and thermal stability, electronic structure, and optical features of In2PtX6(X = Cl, Br, and I) perovskites, utilizing first-principle calculations. The stability is predicted using phonon dispersion spectrum and ab initiomolecular dynamics simulation and also through the convex hull approach. The lattice constants and the optimized volume show an increasing trend with changing halide ions. The band structures computed for In2PtCl6, In2PtBr6, and In2PtI6indicate their semiconducting nature with band gap values of 2.06, 2.01, and 1.35 eV, respectively. Halogens pand Pt dorbitals, respectively, play a prominent role in the formation of states around valence band maximum and conduction band minimum. The compounds, namely, In2PtBr6and In2PtI6, exhibit high dielectric constants and small carrier effective masses. Furthermore, we found that In2PtI6reveals a maximum theoretical efficiency owing to its optimum band gap and high optical absorption and is comparable to MAPbI3in the studied range. Our results suggest that In2PtX6(X = Cl, Br, and I) are suitable materials for single-junction and top absorber layers in tandem solar cells.

A general tight-binding total energy scheme is used to calculate the structural properties of the intermetallic compound Cu3Au in different phases (L12, A15, NaCl, D09and D022). In most cases there is good agreement between our results and experiments. We also investigate the structural properties of different forms of the clusters (CuAu, CuAu2, CuAu3and Cu6Au8).

Simulation methods have been used to study the miscibility ofCuxAg1−xIbased on a Tersoff potential. Monte Carlo calculations show that CuxAg1−xIis a complete solid solution. This result agrees well with experiments using NMR and X-ray diffractions methods. Structural, elastic and thermodynamic properties are also predicted at 0.25, 0.5 and 0.75 using molecular dynamics simulations.

Mixed CuBrxI1-xcrystals are studied for x = 0.25, 0.5 and 0.75 using simulation methods based on a three-body potential. Monte Carlo calculations show that these crystals are solid solutions and are in good agreement with experimental results. Structural and thermodynamic properties are also investigated using molecular dynamics simulations.

By accurately fitting the tight-binding (TB) parameters to ab-initio band structures from different tetrahedral volumes, the TB parameters have been adjusted for germanium. The model has short-range radial form similar to the tight-binding Hamiltonian of Goodwin, Skinner, and Pettifor. However, the properties of the higher-coordinated metallic structures are well described by the model in addition to those of the lower-coordinated covalent structures. This one reproduces accurately the band structures of germanium polytypes (cubic diamond (cd), hexagonal diamond (hd), body-centered-tetragonal (β-Sn), simple cubic (s.c.), body-centered-cubic (b.c.c.), simple hexagonal (s.h.), face-centered-cubic (f.c.c.), and compact-hexagonal (h.c.p.)) and gives a good description of the elastic constants for germanium in the diamond structure.

AbstractMixed CuClxBr1−xcrystals are studied using a Tersoff potential. Structural and elastic properties of the solid solution are calculated and are in good agreement with experiments. Various thermodynamic quantities including thermal expansion coefficient, heat capacity, and Grüneisen coefficient are also predicted.

The cure kinetics of a high molecular weight acid copolymer used as a hardener for a commercial epoxy resin (DGEBA) was studied by DSC. The systems were uncured and partially cured epoxy poly(maleic anhydride-alt-styrene) (PAMS) at different periods of time. The state of cure was assessed as the residual heat of reaction and was varied by controlling both the time and temperature of cure. The conversion degree of crosslinking increased with time and temperature. Additionally, the activation energy and reaction order were calculated by the Freeman–Carrol relation and showed a dependence on the conversion degree of crosslinking. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2089–2094, 1999

We present a transferable tight-binding model; the electronic band structures and density of states of silicon in several cubic forms are obtained, within a nonorthogonal basis. We have fitted the nonorthogonal tight-binding model of silicon with a minimal (s, p) basis. Using a numerical procedure, our parameters were fitted to LMTO band structures in different crystalline phases of silicon (f.c.c., b.c.c., s.c., and h.c.p.). Such fits were performed to obtain a model that we judged to be accurate and should be applicable to many other systems. In addition to a very good fit to the electronic properties of Si in different bulk crystal structures our TB parameters describe very well the elastic constants and the optical phonon frequency at the zone-center in crystalline silicon.

The two-dimensional (2D) layered molybdenum disulfide (MoS2) material represents a nominee potent for optoelectronic devices application. In this research work, the experimental characterizations of 2D- MoS2thin films are reported in terms of various microscopic and spectroscopic techniques. The synthesized MoS2thin films are grown by employing the pulsed laser deposition (PLD) procedure on SiO2/Si substrates. In order to monitor the deposition rates of ablated films, the buffer argon-gas pressures are varied during the pulsed laser deposition at substrate temperature of 700 0C. The field emission scanning electron microscopy and atomic force microscopy analyzes revealed a change in the surface morphology and thickness size of MoS2flakes when the buffer Ar-gas pressure is varied between 0 and 100 mTorr. For all samples, a 2H-phase is revealed from X-ray diffraction patterns, indicating a reflection (2θ) around 14.85°. By varying the deposition pressure of laser-ablated MoS2films, the X-ray photoelectron spectroscopy divulged the chemical compositional elements and valence states of Mo and S on the surface of MS2films with low density of defects. Analysis of the photoluminescence spectroscopy illustrated emission bands spanning from the visible (Vis) to near-infrared (NIR) regimes in the deposition pressures range ∼ 0-100 mTorr. This is mainly owing to the change in the recombination of electron-hole pairs and charge transfer between the deposited MoS2films and SiO2substrate surface under various buffer gas pressures. Additionally, first-principles electronic structure calculations are performed to qualitatively examine the effect of native point-defect species (sulfur-monovacancy and sulfur-divacancy defects) on the electronic structure and optical properties of 2D- MoS2sheets. It is unveiled that the variation of compositional sulfur-vacancy defect in MoS2monolayer creates an in-gap defect levels above the valence states, leading to an acceptor character. Importantly, the enhancement in the optical absorption spectra divulged a shift in the optical gap from Vis-NIR window with the increase of sulfur vacancy contents in MoS2single-layer. The identification of intrinsic point defects may be beneficial for photovoltaic energy conversion at higher wavelengths by designing next generation 2D-semiconductors, which could be of vital significance for growing 2D layers and multilayers into practical technologies.

The optoelectronic and transport characteristics of CsYbX3(X = Br, Cl) are computed for clean energy harvesting. The structural stability has been anticipated by Goldsmith tolerance factor and thermodynamic stability by formation energy. The band gaps 1.66 eV and 1.44 eV for CsYbCl3and CsYbBr3are observed in visible energy region, which show their significance for optoelectronic and solar cells. The dielectric constant reveals the polarization of light while absorption coefficient and imaginary dielectric constant ensure maximum absorption in the visible region. Refractive index appears in the range of 1 to 2 and minimum reflectivity also builds their significance for optical applications. The transport properties are elucidated by electrical and thermal conductivities, Seebeck coefficient and figure of merit (ZT). The high value of ZT makes them equally important for thermoelectric devices.