Perdew Burke Ernzerhof Research Articles

Computational investigation on physical properties of lead based perovskite RPbBr3 (R = Cs, Hg, and Ga) materials for photovoltaic applications

In the modern era, the major problem is solving energy production and consumption. For this purpose, perovskite materials meet these issues and fulfill energy production at a low cost. Density functional theory and the Cambridge Serial Total Energy Package (CASTEP) are used to examine the characteristics of the cubic inorganic perovskites RPbBr3 (R = Cs, Hg, and Ga). In the context of the generalized gradient approximation (GGA), the ultrasoft pseudo-potential plane wave technique and the Perdew–Burke–Ernzerhof exchange–correlation functional are used for investigations. Structural, mechanical, electronics, and optical properties are investigated using CASTEP code. According to structural properties, compounds have a cubic nature with space 221 (Pm3m). Compounds formation energy (− 3.46, − 2.21, and − 3.14 eV)of (CsPbBr3, HgPbBr3, and GaPbBr3) and phonon calculations are studied and find that compounds are stable. The results of our investigation show that the compounds have narrow bandgaps of direct kind, with 1.85 eV for CsPbBr3, 1.56 eV for HgPbBr3, and 1.71 eV for GaPbBr3, respectively, indicating that they may be used to improve conductivity. Additionally, anisotropy (2.135, 3.651, 10.602), Pugh’s ratio (1.87, 2.25, 2.14), and Poison’s ratio (0.27, 0.31, 0.29) are traits that the compounds (CsPbBr3, HgPbBr3, GaPbBr3) display a ductile nature. The CsPbBr3 compound showed significant optical conductivity and absorption in terms of their optical properties, especially in the visible region, which makes them suitable for use in solar cell applications as well as for LED applications.

Study of structural, electronic, optical and mechanical properties of PbZrO3 under stress: a DFT approach

The structural, electronic, optical and mechanical characteristics of PbZrO3 (PZO) at external pressure ranging from 0–550 GPa have been analysed via density functional theory via generalised gradient approximation (GGA) and Perdew–Burke–Ernzerhof (PBE) exchange-correlation functional by applying external pressure up to 0–550 GPa. Band gap of electronic structure gradually decreased (2.434–0.181 eV) as pressure increased, and structure remains cubic at all pressures (0–550 GPa). The ultra-soft pseudopotential technique was applied to analyse the structure of band and its effects at the optical features of PZO in cubic phase. Several mechanical and elastic parameters have been calculated and the results indicate that the material is stiff, inflexible and resistant to shear stress. To confirm that a substance is anisotropic, various anisotropy factors are calculated. Optical properties such as absorption, loss function (L), refractive index (n), reflectivity (R) and the extinction coefficient (k) was computed to determine the impact of external isotropic pressure. PZO is extensively used in optoelectronic devices, it is now possible to employ it in a wide range of electromechanical systems, including infrared detectors, optoelectrical modulators circuits, storage device for memories and capacitors for use in microwave devices with high frequencies.

Electronic Properties of Si and C Substitutional Defects and Porosity in C‐Rich and Si‐Rich Hydrogenated Roundish SiC Quantum Dots: An Ab‐Initio Study

AbstractIn this study, SiC quantum dots (SiC‐QD's) are studied, and some roundish SiC‐QD's with the incorporation of defects by removing a carbon or silicon atom are considered. Fourteen configurations are modeled in which the position of the silicon or carbon defect for each configuration is changed, considering that due to the chemical composition, it allows more Si atoms or more C atoms on the QD surface. All calculations are performed using the Density Functional Theory (DFT) methodology. The electronic exchange correlation is treated using the Generalized Gradient Approximation (GGA) with the Revised Perdew–Burke–Ernzerhof (RPBE) functional. The electronic energy levels of each configuration are calculated as well as the partial density of states to know the origin of the energy gap in each quantum dot. The final step is to analyze the energy formation to determine chemical stability.

Geometric and electronic structures of Cs2BB′X6 double perovskites: The importance of exact exchange

A widely adopted computational protocol in contemporary materials research is to first relax materials' geometries using semilocal density functional approximations (DFA), and then determining their electronic band structures using the more expensive hybrid functionals. This procedure often works well, as the popular semilocal DFAs, such as the Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation, yield rather good geometries for a wide range of materials. However, here we show that, for some of the lead-free halide double perovskites (HDPs) Cs2BB′X6 (B=Ag+, Na+; B′=In3+, Bi3+; X=Cl−, Br−), the validity of this common practice is questionable. We find that, for these HDPs, the geometrical structures, in particular, the B(B′)−X bond lengths predicted by PBE show large deviations from the experimental values. Additionally, the band gaps of some of these materials (specifically, the In-based HDPs) are sensitive to the B(B′)−X bond lengths. As a consequence, the band gaps obtained using the hybrid functionals (such as the Heyd-Scuseria-Ernzerhof functional) based on the PBE geometries can still be quite off, in particular, for HDPs with B′=In3+. The situation is significantly improved by using hybrid functionals with tuned portion of exact exchange, based on the geometries determined consistently under the same level of theory. The successes and failures of several popular exchange-correlation (XC) functionals are traced back to the so-called delocalization error, and can be quantitatively analyzed and understood via a three-atom linear-chain B−X−B′ molecular model. Finally, our findings provide a practical guide for choosing appropriate XC functionals for describing HDPs and point to a promising path for band structure engineering via doping and alloying. Published by the American Physical Society 2024

A DFT study to explore structural, elastic, mechanical, electronic and optical properties of inverse perovskite SbPMg3 for solar cell applications

This study presents the structural, mechanical and optoelectronic properties of inverse perovskite SbPMg3 for optoelectronic applications. The structural optimization is carried out by employing Generalized Gradient Approximation of Wu–Cohen, Perdew–Burke–Ernzerhof and PBE revised for solids. The optimized lattice constant and bulk modulus of SbPMg3 is 4.85 Å and 54.20 GPa with WC-GGA scheme. The positive phonon frequencies are indicating that SbPMg3 is dynamically stable. The mechanical properties were calculated by obtaining elastic constants C11, C12 and C44. The structural stability is evaluated according to Born–Huang stability criteria. The band gap, static dielectric constant and static refractive index is 1.70 eV, 8.23 and 2.87 calculated with WC-mBJ exchange and correlation functional. The band structures show that inverse perovskite SbPMg3 possesses direct band gap nature. The absorption peaks in visible and ultraviolet energy region anticipates that SbPMg3 is promising novel material for optoelectronic applications.

Effect of Ca, Ba, Be, Mg, and Sr Substitution on Electronic and Optical Properties of XNb2Bi2O9 for Energy Conversion Application Using Generalized Gradient Approximation–Perdew–Burke–Ernzerhof

Bismuth layered structure ferroelectrics (BLSFs), also known as Aurivillius phase materials, are ideal for energy-efficient applications, particularly for solar cells. This work reports the first comprehensive detailed theoretical study on the fascinating structural, electronic, and optical properties of XNb2Bi2O9 (X = Ca, Ba, Be, Mg, Sr). The Perdew–Burke–Ernzerhof approach and generalized gradient approximation (GGA) are implemented to thoroughly investigate the structural, bandgap, optical, and electronic properties of the compounds. The optical conductivity, band topologies, dielectric function, bandgap values, absorption coefficient, reflectivity, extinction coefficient, refractive index, and partial and total densities of states are thoroughly investigated from a photovoltaics standpoint. The material exhibits distinct behaviors, including significant optical anisotropy and an elevated absorption coefficient > 105 cm−1 in the region of visible; ultraviolet energy is observed, the elevated transparency lies in the visible and infrared regions for the imaginary portion of the dielectric function, and peaks in the optical spectra caused by inter-band transitions are detected. According to the data reported, it becomes obvious that XNb2Bi2O9 (X = Ca, Ba, Be, Mg, and Sr) is a suitable candidate for implementation in solar energy conversion applications.

Ab Initio Study of Structural, Electronic, Optical, and Thermoelectric Properties of Cs2(Li/Na)GaI6 for Green Energy Applications

The recent year has witnessed a flurry of activities in investigating the promising electronic, optical, and transport properties of lead‐free double perovskite halides. In the present work, the structural, electronic, optical, and transport properties of Cs2(Li/Na)GaI6 are carefully examined. The predicted negative formation energy, absence of imaginary frequency in the phonon spectra, and ab‐initio molecular dynamics calculations show that they are thermodynamically stable. Additionally, electronic studies employing generalized gradient approximation (GGA)–Perdew–Burke–Ernzerhof (PBE) + modified Becke‐Johnson + spin‐orbit coupling reveal that Cs2(Li/Na)GaI6 exhibits a direct bandgap, with values of 1.24 eV for Cs2LiGaI6 and 1.39 eV for Cs2NaGaI6. The exceptional optical properties, including a high absorption coefficient (105 cm−1) and excellent optical conductivity with low reflectivity across the entire UV–visible range, indicate that Cs2(Li/Na)GaI6 are promising materials for solar cell applications. Moreover, the ultralow thermal conductivity, high Seebeck coefficient, and substantial electrical conductivity of Cs2(Li/Na)GaI6 result in a high figure of merit over the temperature range of 200–600 K. Thus, Cs2(Li/Na)GaI6 shows strong potential as both photovoltaic and thermoelectric materials.

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.

Insights into the band gap anomalies of certain bismuth-based chalcogenides through ab initio calculations of structural and electronic properties

Unlike other conventional metal chalcogenides, where the Perdew-Burke-Ernzerhof (PBE) functional tends to underestimate band gaps, bismuth (Bi) chalcogenides, particularly Bi selenides, exhibit a counterintuitive behaviour with band gap predictions that closely align with experimental results. In this study, we report this anomaly in the band gap prediction of specific Bi-based chalcogenides. The structures of these compounds are of significant interest because their electronic band gaps match well with the reported experimental results when using the PBE functional. This unexpected and counterintuitive deviation, observed in this class of materials, offers valuable insights for material scientists studying compounds in this category.

Effect of V-VIB group ternary elements on the properties of Ti2AlM-type O-phases: A first-principles study

Understanding the underlying constitutional mechanisms for the stability of complex phases and comprehending it is crucial to find new materials with desired mechanical and physical properties. In TiAl-alloys with ternary alloying additions orthorhombic phases can form but the effects of different alloying elements on their stability and other properties are only scarcely known. We present a comprehensive study using density functional theory (DFT) within the generalized gradient approximation (GGA) with the Perdew–Burke–Ernzerhof (PBE) method to determine energetic, and mechanical stability criteria and evaluate the electronic densities of states (DOS) and band structures to understand bonding behavior. The stability of Ti2AlM, as a bulk O-phase in ternary TiAl-based systems is predicted by investigating VB (V, Nb, and Ta) and VIB (Mo, W) group elements as ternary addition M. The electronic density of states and band structure indicate that the ternary elements addition causes charge redistribution through the formation of a bond, which significantly alters the stability and mechanical properties. All investigated compounds exhibit negative formation energies and the calculated elastic constants reveal that all are mechanically stable. For the different O-phase types investigated Ti2AlMo is the most stable and Ti2AlV the least stable when comparing energies of formation. The obtained elastic moduli and Pugh's ratios support the idea that Ti2AlM (M = V, Nb, Ta, Mo, and W) O-phases have attractive mechanical characteristics and exhibit ductility. Among all the systems investigated, Ti2AlMo, and Ti2AlW provide the highest increase in B, G, and E values. Based on the elastic constants also indicators for the mechanical properties, such as Poisson's ratio (ν), and Pugh ratio G/B, are calculated. According to our calculations, the brittle Ti2AlV is harder than the ductile Ti2AlMo. Based on the results of the present study, the Ti2AlM type O-phase is considered a promising constituent for designing new materials in the ternary Ti–Al-M system.

Predicting the thermal decomposition temperature of energetic materials from a simple model.

The key factor in designing heat-resistant energetic materials is their thermal sensitivity. Further research and prediction of thermal sensitivity remains a great challenge for us. This study is based on first-principles calculations and establishes a theoretical model, which comprehensively considers band gap, density of states, and Young's modulus to obtain a empirical parameter Ψ. A quantitative relationship was established between the new parameter and the thermal decomposition temperature. The value of Ψ is calculated for 10 energetic materials and is found to have a strong correlation with the experimental thermal decomposition temperature. This further proves the reliability of our model. Specifically, the larger the value of Ψ, the higher the thermal decomposition temperature, and the more stable the energetic material will be. Therefore, to some extent, we can use the new parameter Ψ calculated by the model to predict thermal sensitivity. Based on first-principles, this paper used the Cambridge Serial Total Energy Package (CASTEP) module of Materials Studio (MS) for calculations. The Perdew-Burke-Ernzerhof (PBE) functionals in Generalized Gradient Approximation (GGA) method as well as the Grimme dispersion correction was used in this paper.

Pressure-dependent band gap engineering with structural, electronic, mechanical, optical, and thermal properties of CsPbBr3: first-principles calculations.

In the renewable industry, pressure-dependent CsPbBr3 perovskite has a lot of potential due to its exceptional properties. Present work revealed the mechanical stability of CsPbBr3 between 0 to 50GPa. The bandgap of unstressed CsPbBr3 is 2.90eV, indicating a direct bandgap. Band gap values decrease by increasing external pressure. CsPbBr3 structure showed a direct band gap from 0 to 35GPa and in-direct from 40 to 50GPa. The unit cell volume and lattice constants are substantially decreased. Mechanical parameters, i.e., Young's modulus, bulk modulus, anisotropy factor, shear modulus, and poison's ratio are obtained. Under ambient conditions, the mechanical properties of CsPbBr3 showed ductile behavior and with induced pressure, their ductility has significantly improved. By applying stresses ranging from 0 to 50GPa, the considerable fluctuation in values of dielectric function (imaginary and real), absorption, reflectivity, loss function, refractive index (imaginary and real), and conductivity (imaginary and real), was also identified. When pressure rises, the optical parameters increase and drag in the direction of high energies. Response functions are used to predict the density of states and the phonon lattice dispersion to study the phonon properties. By using the quasi-harmonic Debye model, the thermal effect on the free energy, entropy, enthalpy, and heat capacity were predicted and compared. These results would be useful for theoretical research and indicate how external pressure significantly affects the physical characteristics of CsPbBr3 perovskites, which may open up new possibilities for use in optoelectronic, photonic, and solar cell applications. The structural, electrical, mechanical, optical, and thermal properties of cesium lead bromide (CsPbBr3) are investigated by applying external pressure from 0 to 50GPa, using generalized gradient approximations (GGA) and Perdew-Burke-Ernzerhof (PBE) with CASTEP code built-in material studio by density functional theory (DFT).

A DFT study to explore structural, elastic, mechanical, phonon, electronic and optical properties of halide perovskites AgXF3(X=Be,Ca)$$ {\mathrm{AgXF}}_3\left(\mathrm{X}=\mathrm{Be},\mathrm{Ca}\right) $$ with PBEsol, TB‐mBJ and SCAN functionals

AbstractFirst principles calculations have been performed using full potential linearized augmented plane wave, FP‐LAPW, within Wien2k to elucidate structural, elastic, mechanical, phonon, electronic and optical properties of lead free halide perovskites . The energy volume curve fitting is used to examine structural stability. For structural optimization and mechanical properties, we employed Perdew–Burke–Ernzerhof generalized gradient approximation and PBEsol, revised for solids, exchange and correlation functional. The optimized lattice constant of and is 3.631 and 4.349Å. The elastic constant , and are computed to extract different mechanical parameters like Poisson's ratio, Pugh's ratio, bulk modulus, shear modulus, Young's modulus, anisotropic ratio, Cauchy pressure and shear constant. The mechanical parameters exhibit greater structural, mechanical and dynamical stability of than . The electronic and optical properties are calculated by using TB‐mBJ and SCAN potentials in addition to PBEsol. The electronic band gap of and is 4.71 and 6.01 eV with TB‐mBJ and both perovskites are indirect band gap materials. The optical response of these perovskites against wide range of incident electromagnetic radiation is assessed by calculating absorption, reflection, optical conductivity, dielectric constant, energy loss function and refraction. Strong absorption, high optical conductivity and low reflectivity indicates that and are promising materials for photovoltaic applications.

Effect of strain on the photoelectric properties of molybdenum ditelluride under vacancy defects: a DFT investigation.

This study explores the impact of deformation on the electrical and optical characteristics of monolayer cadmium telluride (MoTe2) with vacancies, using the foundational principles of density functional theory. It was discovered that both strain and imperfections alter the electrical characteristics of monolayer MoTe2. Under VTe-MoTe2, a direct-to-indirect band-gap transition occurs. In DTe-MoTe2, the band-gap value reduces dramatically, the conduction band changes downward, and the carrier concentration rises. The DVTe-induced band gap state is closer to the Fermi energy level than the VTe-induced band gap state. In this paper, DTe-MoTe2 is chosen for tensile deformation. The results show that the band-gap value tends to decrease by increasing tensile deformation. When the stretching value reaches 10%, the lower bound of the conduction band and the top of the valence band overlap, and the system is converted from a semiconductor to a metal. Considering the density of states, the missing state MoTe2 is mainly contributed by the participation of Te-s, Te-p, and Mo-d orbitals. In terms of optical qualities, the absorption and reflection peaks are red-shifted and blue-shifted, respectively. It is hoped that these effects on the optoelectronic properties will be widely applied. In this study, we utilize the generalized gradient approximation plane-wave pseudopotential method, incorporating Perdew-Burke Ernzerhof (PBE) generalized functions and following the fundamental principles of the density functional theory framework. A 3 × 3 × 1 supercell was constructed as an undoped model based on a MoTe2 monolayer, which consists of 9 Mo atoms and 18 Te atoms. The vacuum flat plate was set to 15Å along the z-direction to avoid interactions between the monolayers. For electronic structure calculations, the energy cutoff was set to 450eV. Each model's computational process and structural optimization were carried out using the Monkhorst-Pack specialized K-point sampling approach. Crystal optimization computations used a 3 × 3 × 1 Monkhorst-Pack K-point grid for molybdenum ditelluride monolayers and a 9 × 9 × 1K-point grid for electronic system analysis, analyzing state density and optical characteristics, respectively. For the structural optimization, the convergence requirements for maximum force, maximum atom displacement, maximum stress, and energy change were defined at 0.03eV/Å, 0.001Å, 0.05 Gpa, and 1.0 × 10-5eV/atom, respectively.

An in-depth look at the stability, electronic structure, mechanical properties, and thermodynamics characteristic of Ir3TM (TM: Sc, Ti, V) compounds

In this paper, the structural, mechanical, electronic, and thermodynamic properties of Ir3TM (TM = Sc, Ti, and V) intermetallic compounds in the cubic (L12) and hexagonal (D019 and D024) phases are presented. The outcomes of the simulation rely on density functional theory (DFT) within the Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA) based on the full-potential linearized augmented plane wave (FP-LAPW) approach. The existing study was performed on the L12 cubic phase. in addition to hexagonal D024 and D019 phases, which may be relative but differ in the way that the atomic layers are stacked. The calculated total, cohesive energy, and heat formation suggest that the Ir3Sc compound can be stable in the D024 phase because of an overlap between the L12 and D024 phases with a total energy difference of around 0.026 eV/atom. Ir3Ti and Ir3V are more stable in L12 and D019, respectively. From elastic constants calculations, it reveals that the studied compounds are mechanically stable and harder in the cubic phase than hexagonal phase. However, Ir3Sc has the lowest hardness due to its relative ductility. Inversely, Ir3V has the maximum hardness with a lack of ductility. It was observed that these compounds have an elastic anisotropy based on the three-dimensional Young's modulus surface, and Ir3Sc has the strongest anisotropy, while Ir3V has the weakest in the L12 phase. The total density of state (TDOS) calculations shows that Ir3Ti and Ir3V are stable in the L12 and D019 phases, respectively, except for the Ir3Sc compound which might undergo a martensitic transition. Also, the pseudogap for Ir3V moves quite close to the Fermi level, indicating that the covalent bonding in this compound is sharper than the other compounds. Moreover, via the quasi-harmonic Debye model within the Gibbs computational code, thermodynamic properties are calculated and analyzed with temperature and pressure.

Structural, electronic, mechanical, thermodynamic and optical properties of oxide perovskite BeZrO3: a DFT study

The geometrical, electronic, mechanical, thermodynamic, and optical aspects of BeZrO3 crystal have been investigated employing Generalized Gradient Approximation (GGA) with Perdew–Burke–Ernzerhof (PBE), Revised Perdew–Burke–Ernzerhof (RPBE), Local density approximation (LDA) with Ceperley Alder and Perdew Zunger (CA-PZ) techniques under density functional theory. The band gap values of BeZrO3 have been reported to be 0.603 eV, 0.623 eV, 0.614 eV and 2.20 eV respectively in PBE, RPBE, LDA and Becke, 3-parameter, Lee–Yang–Parr (B3LYP) methods. Total and partial density analysis was used to determine atomic orbital nature of the Be, Zr, and O atoms in BeZrO3. By estimating the Mulliken population charge, the bonding characteristics of BeZrO3 have been elucidated. Using the Born mechanical stability criterion, it was determined that BeZrO3 crystal is mechanically stable. The evaluation of ductile strength was expressed by using Poisson and Pugh’s critical ratios, revealing the inherent elastic anisotropy features. The optical characteristics have been conducted using various methodologies, concluded that BeZrO3 exhibits remarkable efficacy in absorbing ultraviolet and visible light.

Investigation of Structural, Electronic, and Optical Characteristics of a Novel Perovskite Halide, Mg3AsCl3, for Electronic Applications

In the present research article, the structural, electronic, and optical characteristics of a novel perovskite halide, Mg3AsCl3, for a broad range of applications are thoroughly investigated. The characteristics of Mg3AsCl3 perovskite are investigated via the use of the generalized gradient approximation (GGA), Perdew–Burke–Ernzerhof and Heyd–Scuseria–Ernzerhof (HSE06) functionals, which are employed in conjunction with the linear combination of atomic orbital calculator. The structural, electrical, and optical characteristics of the material are investigated using density‐functional theory. In this study of the electronic characteristics, it is found that Mg3AsCl3 exhibits an indirect energy bandgap of 2.49 eV with GGA and 3.54 eV with HSE06. The complex band structure exhibits characteristics that indicate the presence of evanescent waves, which are characterized by a layer separation of 5 Å. The report in this research presents reflectivity values of 0.06328 and 0.02971 with GGA and HSE06 functionals, respectively. The reported values of the extinction coefficient are 3.36487 × 10−5 and 2.07389 × 10−5 calculated with GGA and HSE06 functionals. The value reported for the real dielectric function Re[ε] is 2.79625 with GGA and 2.00658 with HSE06. Overall, in these findings, an overview is given that Mg3AsCl3 holds potential as a candidate for use in a wide range of electronic device applications.

Assessing the viability of hydrogen-based perovskites for optoelectronic and thermoelectric applications via first principle modeling.

In this study, we delve into the physical characteristics of six hydride perovskites of ABH3-type materials (CsCaH3, CsSrH3, KMgH3, LiBaH3, NaBeH3, and RbCaH3). Our investigation primarily focuses on assessing their structural stability by determining the enthalpy of formation and examining the dispersion of phonons. Using band structure calculations, we discern the characteristics of semiconductors, observing a direct bandgap in all four perovskites except NaBeH3 and KMgH3, which exhibit indirect gaps. Among these, NaBeH3 possesses the narrowest gap at 1.91 eV, while the widest gap is observed in the perovskite RbCaH3, measuring 4.56 eV. Furthermore, we conduct a thorough analysis of their optical properties, including parameters such as the real and imaginary dielectric function, absorption coefficient, and refractive index within an energy range of 0 to 14 eV. The results of our study are highly encouraging, suggesting that these materials hold significant promise for utilization in photovoltaic cells. This is primarily attributed to their remarkable ability to absorb light across both the ultraviolet (UV) and visible spectra. Additionally, we conducted an assessment of the thermoelectric properties of the six perovskite materials. RbMgH3 exhibits a maximum Seebeck coefficient (Smax) of 1.5 mV/K, whereas KMgH3 achieves a figure of merit reaching unity. These findings present promising opportunities for utilizing these compounds in thermoelectric devices. In this study, all self-consistent field (SCF) calculations were performed using density functional theory (DFT), employing the FP-LAPW + lo method as implemented in the Wien2k code. The Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation, the modified Becke-Johnson (mBJ) methods, and the HSE06 hybrid functional were employed to characterize the exchange-correlation interactions. Thermoelectric parameters were extracted using the BoltzTraP software.

A DFT study on structural, electronic, and optical properties of cubic perovskite semiconductors InXF3 (X = Be and Ca) for optoelectronic applications

First principles calculations were employed to study the structural, electronic and optical properties of Indium based cubic perovskite materials, specifically focusing on InBeF3 and InCaF3 compounds. The generalized gradient approximation Perdew–Burke–Ernzerhof (GGA_PBE) approximation and Tran–Blaha modified Becke–Johnson (TB-mBJ) approximations were used to study and compare the electronic and optical properties. The compound InBeF3 is predicted to have an indirect band gap of 2.51 eV in GGA_PBE and 2.96 eV in TB-mBJ. InCaF3 is found to have a direct wide band gap of 3.61 eV in GGA_PBE and 4.37 eV in TB-mBJ approximation. The partial density of states predicts the significance of In-5p and F-2p states in the conduction and valence bands, respectively. The dielectric constants decrease under the TB-mBJ approximation, with InCaF3 demonstrating lower values owing to its larger band gap. Optical activity analysis indicates transparency for both compounds with notable absorption peaks, suggesting potential applications in transparent coatings. Refractive indices decrease with photon energy, with values dropping below 1.0 in the TB-mBJ approximation, indicating superluminal behavior in wave propagation. The drop in refractive index value below1.0 is earlier for InCaF3 than InBeF3. Examination of the extinction coefficient reveals UV absorption peaks, indicating potential for optoelectronic applications. From this study it can be noticed that the compounds under study can be used for optoelectronic applications, supported by their predicted structural and optical properties study.

Density Functional Investigation of [001] and [111] SiNWs and the Effect of Doping with Boron and Phosphorus

In the present study, we investigate the influence of boron (B) and phosphorus (P) (p- and n-type, respectively) doping on the electronic properties of ultra-thin silicon nanowires (SiNWs) by gradient-corrected density functional calculations with the Perdew–Burke–Ernzerhof (PBE) approximation. In the limit of very small diameters (5–8 Å), both pristine and highly active unsaturated SiNWs with orientations along the [001] and [111] directions exhibit electronic states around the Fermi level, indicative of conductive properties. Conduction is further enhanced by the introduction of doping atoms, as demonstrated by the relative change in the band structures of SiNWs with and without B and P doping. This investigation provides an important insight into the electronic states of SiNWs, which are candidates for future electronics or sensing applications.