WIEN2k Code Research Articles

Effect of oxygen content on structural and optoelectronic properties of ZnS1- xOx alloy in the wurtzite structure

The tunability of the physical parameters of ZnS1-xOx alloy in the wurtzite phase makes this semiconductor potentially useful as an absorbent layer and antireflection coating. A deviation of the bulk modulus from Vegard's law is observed in ZnS1-xOx alloy. Based on the density functional theory as implemented in the Wien2k code under the virtual crystal approximation, the lattice constant, bulk modulus and band gap have been calculated with both GGA and the modified Becke-Johnson potential (mBJ). The ternary ZnS1-xOx alloy becomes more stable with the increase in the oxygen content x. The in-plane and out-of-plane imaginary components of the dielectric function attain non-zero magnitude at energy identical to the fundamental band gap value. The intense peaks in the in-plane and out-of-plane dielectric function located at 6.5 eV and 7.75 eV suggest inter band transition, and no photon emission in this material. ZnS1-xOx absorbs ultraviolet light in the range 4 eV–10 eV, which validates its candidature for optical and photovoltaic devices. The refractive index is more important when photons move through the material and when bonds between atoms are covalent. The anisotropic optical parameters, the fundamental band gap range (2.7–3.7 eV) and absorption of extreme ultraviolet light make ZnS1-xOx alloy as windows, lenses and absorber material.

Structural, elastic, electronic, optic and thermodynamic properties of Li2BaSnX4 (X= S and Se) alloys: A first-principle study

The structural, elastic, electronic, optic and thermodynamic properties of Li2BaSnS4 and Li2BaSnSe4 compounds are investigated by mean of the DFT-based FP-LAPW method as implemented in the Wien2k code. The exchange-correlation potential is treated with the GGA-WC approximation and the TB-mBJ approach. A volume optimization showed that the stannite structure is the most stable phase. The predicted structural parameters are in good agreement with the available experimental data. The independent elastic constants are calculated and used to verify the mechanical stability. In addition, the other elastic parameters such as the shear modulus, Young's modulus, Poisson's ratio, anisotropy factor, Lamé’s constant and Pugh indicator are calculated. Electronics calculations reveal that our compounds are of a direct band gap semiconductor. The important optical functions such as the dielectric function, absorption coefficient, refractive index, and reflectivity have also been calculated and discussed and indicated that both compounds show weak transparency with a considerable reflectivity in the ultraviolet spectral domain. The thermodynamic properties such as the heat capacities, the coefficient of thermal expansion and the Debye temperature are also investigated, in the pressure range from 0 to 30 GPa and the temperature interval from 0 to 700 K.

Revealing excellent electronic, optical, and thermoelectric behavior of Eu based EuAg2Y2 (Y= S/Se): For solar cell applications

We have investigated the structural, electronics, optical, and thermal properties of Eu-based Zintl phase EuAg2Y2 (Y= S/Se) compounds using density functional theory as implemented in WIEN2k code. According to our observations, these compounds are dynamically stable in trigonal crystal structure with no negative frequencies in the phonon spectra. Both compounds EuAg2Y2 (Y= S/Se) possess a direct bandgap of 2.06 eV and 1.71 eV respectively which lies in the visible region. The optical response of EuAg2Y2 (Y= S/Se) compounds shows that the materials exhibit maximum absorption and minimum energy loss in the visible range, making them more viable and promising for optoelectronics and solar cell systems. We have also analyzed the thermal behavior of the compounds using BoltzTrap which was implemented in the WIEN2k code that includes Seebeck coefficient, electrical conductivity, thermal conductivity, and power factor. The maximum power-factor 0.77 × 1011 W/K2ms, 0.47 × 1011 W/K2ms at room temperature is obtained for EuAg2Y2 (Y= S/Se) compounds. The high-power factor at high temperature suggests compounds have a significant thermoelectric characteristic that could be used in renewable energy devices.

DFT study of the structural, elastic and optoelectronic properties of Cu-based cubic halide-perovskites ACuF3 (A = Mg and Ca)

Copper based halide-perovskites ACuF3 (A = Mg and Ca) have been studied for potential application as an electrode material. Structural, electronic, elastic and optical properties of these compounds are investigated by utilizing the wien2k code within density functional theory. Structural study reveal that both compounds have stable and cubic perovskite structure with optimized lattice constants 4.07 Å and 4.15 Å having space group pm-3m 221. Electronic analysis reveals that both compounds have metallic nature. Through IR-Elast package the elastic constants are evaluated and by utilizing these constant various elastic parameters like bulk modulus, shear modulus, Kleinman parameter, Anistropic factor are analyzed. Both compounds are found to be mechanically stable with ductile nature. Furthermore, the various optical parameters such as dielectric function, refractive index, optical conductivity, reflectivity and absorption coefficient are studied. The seebeck coefficient, electrical conductivity and electronic thermal conductivity are studied through BoltzTrap. The study reveals that MgCuF3 and CaCuF3 can be potential candidates for electrode materials.

Ab-initio study of half-metallic ferromagnetism and transport characteristics of MgV2S/Se4 spinels for spintronics and thermoelectric applications

Understanding ferromagnetism and thermoelectric behavior are crucial in spintronics and thermoelectric device applications. Using density functional theory-based WIEN2k code, we have examined the physical properties of vanadium-based MgV2S/Se4 spinels. The calculated negative formation energies and positive phonon frequency indicate the stability of the studied system. The lowest energy ground state has been predicted to be a ferromagnetic phase. The calculated electronic band structure and density of states show that these materials are half-metallic ferromagnetic. The existence of the ferromagnetic phase is described using the pd hybridization, double exchange interaction model by computing the exchange energy and constants. In addition, the quantum coupling of electrons is caused by the shift of the magnetic moment from the V site to non-magnetic sites (S/Se, Mg). Finally, electronic transport parameters like the Seebeck coefficient, electric and thermal conductivity, and power factor are also determined.

Emerging Study on Lead‐Free Hybrid Double Perovskite (CH3NH3)2AgInBr6: Potential Material for Energy Conversion between Heat and Electricity

Minimal cost, huge area, high throughput, high performance of photovoltaic panels, prolonged lifespan, and less toxicity are vital aspects when transitioning photovoltaic technology from lab‐scale production to industrial implementations. A new class of materials typically known as hybrid halide double perovskites (HHDPs) has emerged as a possible alternative for the replacement of toxic lead in crystal lattice for realizing lead‐free, stable, and high‐performance perovskite solar cells (PSCs). An ab initio analysis of (MA)2AgInBr6 HHDP via the WIEN2K code is conducted. It is found that this material has a direct bandgap of 3.85 eV having excellent optical properties in the UV region. The calculated thermodynamic parameters confirm its thermal stability at different temperatures and pressure. Its figure of merit is more than unity at room temperature as well as higher temperature ranges, so this material will be useful in thermoelectric (TE) devices as a TE material.

Investigation of electronic structure, magnetic stability, spin coupling, and thermodynamic properties of novel antiferromagnets XMn2Y2 (X = Ca, Sr; Y = P, As)

In the present work, the structural, electronic, magnetic, and thermodynamic properties of ternary compounds of composition XMn2Y2 (X = Ca, Sr; Y = P, As) are reported. The calculations are performed using the full potential augmented plane wave method (FP-APW) within the framework of density functional theory (DFT) as integrated with the WIEN2k code. The volume optimization is performed for different spin configurations to obtain the optimized unit cell structure, using the minimum energy considerations. It is found that the studied systems favor the antiferromagnetic (AFM) structure. Calculated structural parameters are in good agreement with the existing data. Based on their band structures and density of states (DOS), CaMn2P2, SrMn2P2, and SrMn2As2 have a metallic character, while CaMn2As2 is a semiconductor with a narrow band gap of 0.1161 eV on using GGA and as metallic when GGA+U is employed. The density of states diagrams show that the Mn-3d state contributes majorly to the valence band and the lower part of the conduction band. From stable geometries of XMn2Y2 compounds, it is evident that the Mn atoms are coupled antiferromagnetically in all the compounds. The large value of TC for CaMn2As2 shows strong correspondence among the magnetic atoms. Owing to their suitable magnetic characteristics, these compounds can be used in applications such as Colossal magnetoresistance (CMR) or Giant magnetoresistance (GMR), single-molecule magnets, read heads, spin filters, spin valves, magnetic sensors, and in spintronics applications. Furthermore, temperature and pressure dependence of thermodynamic properties of these materials have been examined in the ranges (0–800 K) and (0–18 GPa), respectively.

DFT and experimental investigations on CdTe1-xSex for thermoelectric and optoelectronic applications

The optical and electronic characteristics of CdTe-based semiconductors play an important role in modern optoelectronic devices. In the current study, pure and Se doped CdTe compositions were theoretically investigated through density functional theory within the framework of Wien2k code using a modified Becke–Johnson technique. Experimentally CdTe1−xSex (x = 0, 3.125 %, 6.25 %, and 12.5 %) uniform and evenly distributed thin films were successfully deposited through a chemically derived sol-gel-based spin coating technique. The morphological, electronic, thermoelectric, and optical properties were studied through comparative simulations and experimental investigations. Ab-initio and experimental results reveal the similarities and correlation among the findings. The experimental energy band gap was found to reduce from 1.84 eV for pure CdTe to 1.55 eV by incorporation of Se in the pristine CdTe structure. The thermoelectric response in terms of electrical conductivity, Seebeck coefficient, thermal conductivity, and specific heat was recorded and a significant variation was observed. The optical parameters show an enhanced trend in the visible regime with the incorporation of Se content in structure. Absorption coefficient and real epsilon were shown to a sharp increase with increment of Se content. The outcomes of this work are considered that Se containing CdTe composition are promising candidates for enhanced thermoelectric and optoelectronic applications.

Theoretical Investigation of Ferromagnetism and Optical Properties of CuCr2X4 (X = S, Se) Spinels via Ab-initio Calculations

The spintronics technology improve the spin functionality which captivated the existence of ferromagnetism. The control of magnetic properties by electrons spin and transport effect have been illustrated in CuCr2X4 (X = S, Se) spinels DFT through Wien2k and BoltztraP codes. The negative formation of energy established the thermodynamic stability of the examined spinels. The half metallic ferromagnetism in the analyzed spinel’s assures density of states. Magnetic moment (Integer value) and the insulating nature with down spin is the reaction of 100% spin polarization. The negative attainment of the condition have presented the prevailing part of electrons spin to create ferromagnetism.

Computational delving into conceivable thermoelectric and spintronic applications of NH4AF3 (A = Fe and Co) ferromagnets

In this investigation, the structural, mechanical, electronic, magnetic, and thermoelectric properties of fluoroperovskite NH4AF3 (A = Fe and Co) compounds were determined utilizing the WIEN2k code. The structural properties such as tolerance factor, enthalpy, and elastic stability criterion predict that the studied compounds are mechanically and thermodynamically stable. Furthermore, the mechanical properties show that NH4FeF3 is more stretchable and rigid in nature than NH4CoF3. Interestingly, both compounds exhibit the anisotropic, intermediate type of bonding effect, higher plastic deformation limit, and brittle nature. The high melting temperature of the present compounds indicates the possible usage of these compounds in high-temperature electronic applications. The electronic calculations show that NH4FeF3 and NH4CoF3 are half-metallic and ferromagnetic compounds with a combination of ionic and covalent bonds between the different atoms. The thermoelectric parameters predict that electrons are the main charge carriers for the present compound with p-type character. Our study suggests that these plausible applications of the compounds are very versatile and include heat sensors, spintronic devices, optoelectronic sensors, and magnetic tunnel junction devices.

Structural, Thermal, and Electronic Investigation of ZrCo1-xNixBi (x=0, 0.25, 0.75, and 1) Half-Heusler Alloys

This article presents the theoretical evaluation of the structural, mechanical, thermal and electrical properties of half-Heusler (ZrCo1-xNixBi = 0, 0.25, 0.75 and 1) alloys in the framework of density functional theory (DFT) that is implemented in WIEN2k code. Equilibrium lattice parameters are found agree with previous literature. Several calculated mechanical properties are revealed that all studied alloys are mechanically stable. According to the critical values for B/G, Ni-doped ZrCoBi alloys are ductile, whereas ZrCoBi and ZrNiBi are brittle. The band structure and density of states of the present compounds show that ZrCoBi has a semiconducting nature, while Ni-doped ZrCoBi has a half-metallic nature. The structural reforms, brought to ZrCoBi as the Ni-dopant concentration increases at the site of Co-atom, showed an increase in its metallicity, conductivity and ductility, and a decrease in its rigidity, stiffness, minimum thermal conductivity, melting and Debye temperatures. According to the results obtained, ( ZrCo1-xNixBi = 0, 0.25, 0.75 and 1) alloys could have potential thermal and electronic applications.

Several factors influencing energy-loss near-edge structure calculations using Wien2k.

Electron energy-loss spectroscopy (EELS) is widely applied combining with transmission electron microscopes with high spatial resolution, but its interpretation is a challenging task. One of the reasons is that the factors affecting EELS are very complicated. In this paper, we focus on the several factors involved in density functional theory (DFT) calculations. The sensitivity of calculated energy-loss near-edge structure (ELNES) to spin order, pressure and on-site Coulomb energy U has been discussed. Since EELS technique detects the local environment of atoms, the influence of spin order cannot be ignored. The chemical shifts and peak intensity of ELNES are also closely related to corresponding pressure. The correlation effects are very important for transition metal compounds and play a key role in EELS simulations. An overview of the effects of these factors on the ELNES is presented with the help of Wien2k code. The antiferromagnetic order results in the decreasing of intensities of related peaks and the moving of the peaks to high energy loss. The decreasing of lattice parameters causes the ELNES peaks to shift to high energy loss, and the peak shifts at the higher energy loss are more significant. The increase of correlation effect leads to the ELNES peaks to shift to high energy loss accompanied by the increase of the relative intensity of the peaks which locate at higher energy loss. Our work helps to understand how these factors affect EELS and to explain and predict the experimental EELS spectra. Through the discussion of these factors, we propose that some factors could not be ignored in EELS simulations.

Effects of uniaxial strain on structural, electronic, and optical properties of LiNbO3: Ab-initio calculations

The semiconductor LiNbO3 has recently attracted a great deal of interest in the material science community. In this study, the effect of uniaxial strain Ɛc on the structural and optoelectronic properties of the material is studied by the first-principles full-potential linearized augmented plane wave method. The results are obtained in a density functional theory (DFT) framework, using a generalized gradient approximation (GGA-PBE) based on total energy minimization, as implemented in the WIEN2k code. The research results show that the unstrained LiNbO3 is an indirect band gap semiconductor with energy of 3.544 eV, which improves the results of some previous DFT calculations, but is still lower than the experimental data. It is found that the strain between −8% and +8% will affect the value of the LiNbO3 band gap. In fact, the results show that the electronic properties are closely related to the external compressive and tensile stress (CTS), causing the electronic band gap of LiNbO3 to increase and decrease, indeed the gap energy goes from 3.119 eV for 8% to 3.746 eV for −8%. The optical coefficients in the in both x-z directions are studied. For unstrained LiNbO3 they are similar but significantly distinct. The applied uniaxial strain increases the anisotropy significantly, and the difference between the xx and zz directions becomes much larger. It has also been found that strain can cause considerable changes in the optical band gap of the material. In addition, the absorption capacity and optical conductivity is improved under tensile stress, which is more efficient and more suitable for optical applications in the visible and ultraviolet spectrum.

First principle study of optoelectronic and thermoelectric properties of (Cs/Rb) AuI3 for clean energy

The perovskite halides are emerging materials for optoelectronic and clean energy applications.Therefore, we explored the electronics, optical, and transport properties of RbAuI3 and CsAuI3 by density functional theory based on the Wien2k code. The band gaps 0.93 and 0.84 eV for RbAuI3 and CsAuI3, respectively are computed by modified Becke and Johnson potential. The minimum reflection and maximum absorption of light in the infrared to the visible region increase their importance of remote sensing and surgical equipment. The transport properties are comprehensively studied in terms of electrical conductivity, thermal conductivity, and Seebeck coefficient by BoltzTraP code. Thermoelectric efficiency is calculated by the figure of merit (ZT) that is higher for RbAuI3 than CsAuI3.

First-principles calculations on mechanical properties of Rh2MnZn Heusler alloy

Heusler alloys are a huge family of binary, ternary and quaternary compounds and contain a wide range of unique properties, which made Heusler compounds to be the efficient materials for diverse applications. When it comes to the commercial applications mechanical properties are worth of check on and turn out to be the significant factor in the processing and final use of the materials. These properties make the study proficient by examine the nature of material under external pressure. In this study, we estimated mechanical properties of Rh2MnZn full-Heusler alloy using the full-potential linearized augmented plane wave method (FP-LAPW) method within the density functional theory (DFT). We have obtained C11, C12 and C44 elastic constants due to cubic symmetry using Charpin method implemented in Wien2k code. Further, using these elastic constants mechanical properties such as bulk modulus, shear modulus, Young’s modulus, Poisson’s ratio, anisotropic factor and Cauchy’s pressure are calculated. These moduli depicted hardness, ductility and elastic anisotropy of the alloy.

An efficient and stable lead-free organic–inorganic tin iodide perovskite for photovoltaic device: Progress and challenges

Hybrid halide perovskites are an outstanding family of materials for a wide range of optoelectronic applications due to their unique optical and electrical properties. Lead-based chemicals, which are harmful to the environment, are used to attain high power conversion efficiency. Here, carried out the modeling and simulation for fundamental and photovoltaic analysis of a non-toxic formamidinium tin iodide [HC(NH2)2SnI 3] perovskite, via the first-principles method executed in WIEN-2K code with WC-GGA potential. Direct energy bandgap 1.34 eV (at symmetry point R), Optical (dielectric constants, refractive index, absorption coefficient), Elastic parameters (Pugh ratio B/G ∼ 2.21, anisotropic index A ∼ 0.54) reveals that FASnI 3 have a semiconductor nature and have broader visible absorption spectrum with mechanically stable. For the performance of photovoltaic device simulation, the AMPS-1D (Analysis of Microelectronic and Photonic Structures-one dimensional) have been used. The essential absorbance parameters, such as band gap, defect density, thickness, doping concentration, and operating temperature have been used. Furthermore, Electron transport layer (ETL) and Hole transport layer (HTL) like as, ZnO/ZnTe/ZnSe/ZnS/CdS have been investigated and calculated efficiencies are 25.3/24.2/24.4/18.1/22.5%, respectively. Additionally, for calculation of photovoltaic efficiency, the Spectroscopic Limited maximum Efficiency (SLME) metric has been used and computed efficiency is 28.37% at room temperature with 300 nm thickness. The present research offers a new perspective; which is of great impact as far as enhancement of the quality of crystallization of perovskite-based on the tin and involving the improvement of the performance of non-toxic perovskite solar cells (PSCs).

First-principles calculations to investigate structural, elastic, electronic and optical properties of A2OsH6 for storage hydrogen and optoelectronic devices

This work presents an ab-initio study on the structural, elastic, electronic, and optical properties of the hydride compounds A2OsH6 (A = Ca, Ba, Mg, and Sr) using FP-LAPW method with potentials based on DFT, which is implemented in the WIEN2K code. We used a generalized gradient approximation (GGA-PBE, GGA-PBEsol) to describe the exchange-correlation potential. The structure parameters are in good agreement with the experiment. All materials under focus are stable, mechanically and dynamically, and exhibit a ductile behavior. The bandgap is indirect for all studied materials by calculating the DOS state density and band structure. Optical investigations demonstrate that the compounds exhibit good optical conductivity and absorptivity when high-energy photons are incident on their surfaces. Based on these findings, we believe that hydrides fall under the semiconductor category of materials, making them appropriate for use in the storage of hydrogen and optoelectronic devices.

Electronic and Heat Capacity Calculation of Valence Fluctuating YbPd Single Crystal

Inventive calculations were executed for electronic and heat capacity calculations of valence fluctuating YbPd single crystal. By means of Wien2k code, this study has been acted upon. Having a rich variety of physical phenomena, YbPd compound focused to a great extent attention. This compound publicized peculiar possessions attributable to the mixed valence state of the Yb ion. The deliberated bend over of the primary band cram agreed well with the available consequences.

First-principles calculations to investigate structural, electronic and phonon properties of sodium bromide (NaBr) and sodium iodide (NaI) crystals

In this paper, the first-principles study is performed to calculate the structural, electronic and phonon properties of alkali halides NaBr and NaI. The calculations for structural and electronic properties have been carried out using the full-potential linearized augmented plane-wave (FP-LAPW) method that is employed in the WIEN2k code, whereas the phonon properties are studied using the Quantum Espresso program based on density-functional theory within plane-wave fundamental sets and pseudo-potentials approaches. The calculation of structural, electronic band properties were carried out using generalized gradient approximation (GGA), local-density approximation (LDA) and a combination of modified Becke-Johnson exchange potential with LDA and GGA (TB-mBJ-GGA/LDA) for exchange-correlation potential. The calculated structural parameters are in good agreement with experimental results. In our electronic calculations, the obtained bandgaps are underestimated by LDA and GGA functionals compared to empirically derived results, which is an expected result. However, the calculated bandgaps by the modified Becke-Johnson exchange potential are in perfect agreement with the experiment. Finally, the dynamic properties of NaBr and NaI compounds were investigated. Both phonon dispersion and phonon density of states curves were calculated for compounds along with the high symmetry directions in the Brillouin region. The dynamical properties of NaBr and NaI crystals are analyzed and discussed.

First-principles calculations for fundamental and spectroscopic screening of hybrid perovskite (HC(NH2)2PbI3) formamidinium lead iodide

Formamidinium lead iodide [(HC(NH2)2PbI3] material has generated significant interest in their inherent properties and extensive scope of prospective applications. Here, we have successfully computed the structural, electronic, optical, thermal, thermoelectric and elastic properties with the framework of density functional theory over the PBE-sol and WC potential approximations using the WIEN2K code. These explorations show that this material is a direct bandgap semiconductor (1.30 eV), with high absorption coefficients and better thermal stability. The dielectric function and absorption spectra peaks reveal in the IR-visible-UV energy region show the significant future of this material to be used in photovoltaic (PV) devices. Thermal properties have been calculated by GIBBS2 at different temperatures (0–800 K) and pressures (0–8 GPa). Boltztrap with constant relaxation time approximation has been used for computing the thermoelectric parameters at different temperatures (300–800 K). Seebeck coefficient decreases with increasing temperature, electrical conductivity nearly constant in the whole temperature ranges, electrical thermal conductivity increases with increasing temperature, power factor and figure of merit's are also increasing with increasing temperature at a given electron and hole concentration (1018-1019 cm−3). We have also carried out the calculations of spectroscopic limited maximum efficiency (SLME) parameter (39.09%). Moreover, for mechanical stability, we have determined the elastic properties (C11, C12, C44), bulk modulus (B), Young's modulus (Y), shear modulus (G) and stability constants B/G ratio, and Poisson's ratio (ν). These computed results show that the FAPbI3 is a relevant material to be used as an alert substance in photovoltaic device fabrications and proposed outcomes are in good acceptance with the experimental and other theoretical data.