Linear Augmented Plane Wave Research Articles

Exploring the structural, electronic, optical, and thermoelectric properties of potassium-based double perovskites K2AgXI6 (X = Sb, Bi) compounds: A DFT study

Currently, lots of studies are going to find out the quality of the materials that could be used in solar cells and energy storage devices because of their higher absorption and utmost conductivity. We used density functional theory simulations utilizing the full potential linear augmented plane-wave approach. The generalized gradient approximation functional intended for materials (PBE-GGA) was utilized to compute structural characteristics, although the modified Becke and Johnson (mBJ) potential functional was employed to compute optoelectronic and thermalproperties. Their band gaps, may capture electromagnetic waves in the IR to the visible spectrum, rendering them appealingfor optoelectronics devices. Achieving the highest values of transition in the visible region against photon energy in the optical characteristics suggested that investigated double perovskites could be used in solar cells. Additionally, the transport characteristics premeditated using the Boltzmann transport equation indicate that the temperature and chemical potential in K2AgSbI6 to K2AgBiI6 perovskites might be used to make them suitable for solar energy. In order to investigate the optoelectronic as well as thermoelectric characteristics of K2AgXI6 (X = Sb, Bi)compounds used in energy storage devices.

Electronic and optical properties of quaternary selenides for optoelectronic applications: Insights from DFT+U‐computations

AbstractThe optical properties, electronic charge density, electronic structure of the new layered selenides materials, BaGdCuSe3, CsUCuSe3, CsZrCuSe3, and CsGdZnSe3 compounds have been calculated by using the full potential and linear augmented plane wave (FP‐LAPW) methods as applied in the WIEN2k package, which is based on the density functional theory. The ALnMSe3 compound's structure of these was (A = Cs, Ba; Ln = Zr, Gd, U; M = Cu, Zn) is composed of (n = 1, 2) layers, which might be separated by A atoms. It is to be observed that there is strong hybridization between the s, p, and d states of Zr, Gd, and Cu atoms. Around the gadolinium atom, the charge density contours are completely circular, but the Gadolinium “Gd” atom shows an ionic nature. To calculate the refractive index, we used Kramer's Kronig correlations with the imaginary part dielectric function. The decrease in the refractive index is due to the lack of probability for direct excitation of the electrons, resulting in a loss of energy. The value of the static refractive index for all reference compounds is about 1.75–2.25, which is indication that the material used in optoelectronic devices.

Adaptively compressed exchange in the linearized augmented plane wave formalism

We present an implementation of the adaptively compressed exchange (ACE) operator in the linearized-augmented plane waves formalism. ACE is a low-rank representation of the Fock exchange that avoids any loss of precision for the total energy. Our study shows that this property remains in the all-electron case, as we apply this method in nonrelativistic total-energy calculations with a hybrid exchange-correlation functional PBE0. The obtained data for light atoms and molecules are within a few $\ensuremath{\mu}\mathrm{Ha}$ of the precise multiresolution-analysis calculations. Aside from ACE, another key ingredient to achieve such a high precision with Fock exchange was the use of high-energy local orbitals. Finally, we use this implementation to calculate PBE0 gaps in solids and compare the results to other all-electron results.

Theoretical prediction of doping iron ions effect on the optoelectronic and magnetic cobalt-based perovskite (Co1-xFexScO3)

The ab-initio framework has taken place by means of the Full-potential Linear Augmented Plane-Wave (FP-LAPW) method, using the modified Becke-Johnson exchange potential approximation. This modified method was carried out to study the effects of doping iron ions on the structural, electronic, magnetic, and optical properties of CoScO3 perovskite compound. Doping Fe ions have formed a nonstoichiometric perovskite Co1-xFexScO3 where x = 0, 0.25, 0.50, 0.75, and 1. all doped compounds crystallized in a tetragonal lattice due to the Jahn-Teller effect, while the lattice constant was calculated and found to vary between the value of the two pure compounds. Meanwhile, the stabilities of the studied compounds are shown in the negative values of the formation energy. The magnetic moment was calculated and the whole compounds showed a ferromagnetic behavior. Co1-xFexScO3 perovskite is a potential candidate for spintronic application due to the presence of the half metallic behavior. All optical spectrums including dielectric function, absorption coefficient, reflectivity and refractivity index, and energy loss function show remarkable features for the proposed perovskites.

Physical characteristics of Pb1-xAxSe (A=Fe, Mn, V) for spintronic applications

The full-potential linearized-augmented plane wave (FP-LAPW) technique within Density functional theory (DFT) is used to compute the electronic, optical, and magnetic features of Fe, Mn and V doped binary compound PbSe. The effect of doping on energy band gap (Eg) and density of states (DOS) has been studied in detail. The computational results of DOS and band structure (BS) have confirmed that PbSe compound exhibit half-metallic ferromagnetic (HMF) nature. The Eg of PbSe binary compound is 0.16 eV which is enhanced up to 0.35, 0.23 and 0.54 eV after doping of Fe, Mn and V, respectively. Moreover, optical properties of Fe, Mn and V doped PbSe has been also studied in term of dielectric constants, absorption coefficient α (ω), extinction coefficient k (ω), refractive index n (ω) and reflectivity R (ω). The magnetic properties are calculated and it is computed that Pb0.75Mn0.25Se has greater magnetic moment (μB) as compared to Pb0.75Fe0.25Se, and Pb0.75V0.25Se. All the results revealed the appropriateness of Pb1-xAxSe (A=Fe, Mn, V) materials for spinelectronics and optical gadgets.

Mechanical, thermal, electronic, and magnetic properties of Ca0.75Er0.25S alloy from a DFT approach: A promising material for spintronic applications

This paper presents a systematic study of the calculated mechanical properties, electronic structures and magnetic moments of dilute magnetic semiconductor Ca1−xErxS (x = 25 %) using the density functional theory (DFT)-based the full potential linear augmented plane-wave (FP-LAPW) method. The exchange and correlation potential is treated by the generalized gradient approximation GGA-PBE frameworks, which are utilized to characterize the structural and elastic properties of Ca1−xErxS. Moreover, the GGA-PBE +U and mBJ-PBE+U were also applied for the electronic and magnetic properties. To understand magnetic ground state the energy difference in ferromagnetic (FM) and anti-ferromagnetic (AFM) configurations was calculated. The calculated band structure improves when GGA-PBE+U and the modified Becke-Johnson approach (mBJ-PBE+U) methods are employed. The electronic structure analysis reveals that GGA-PBE predicts Ca1−xErxS ternary alloy to be metallic while GGA-PBE +U and mBJ-PBE+U predicts it to be half metallic ferromagnetic with 100 % spin-polarization at the Fermi level, with magnetic moment of 2 μB per formula unit and a band gap 1.90 and 2.40 eV, respectively. Our results indicate that identical magnetic ground states are obtained GGA-PBE +U and mBJ-PBE+U and the magnetic moment mainly arises from 4 f of Erbium (Er). To our knowledge, this is the first time that the physical properties of Ca0.75Er0.25S have been reported, and with consequence the present results can provide the data support for experimental and other theoretical investigations.

Insulator–metal phase transition in novel Sr2OsTiO6 double perovskite via doping - Computational FP study

The structural, electronic, bonding, magnetic, optical and thermal properties of parent perovskite namely SrTiO3 (STO) and novel double perovskite namely Sr2OsTiO6 (SOTO) compounds are analyzed by using Full Potential (FP) - Linearized Augmented Plane Wave (LAPW) method through WIEN2K code. The optimized lattice parameter, bond length, bond angles, Fermi energy (EF), Density of States (DOS) at Fermi Level (FL), electronic specific heat coefficient are computed for the optimized STO and SOTO compounds. At ambient condition SrTiO3 is behaving as a semiconductor with a band gap 1.966 eV and via doping of SrOsO3 and SrTiO3, the resultant product of double perovskite phase namely Sr2OsTiO6 is shifted from the semiconductor state to a normal conductor state. Electron density plots, band structure plots and DOS are illustrated and compared for both STO and SOTO compounds. Diverse bonding and electronic band characteristics are noted and compared. Our band structure calculation results are reveal that the possibility of Electronic Topological Transition (ETT) in these compounds under the effect of doping. Since there is a predominant variation over the structural, electronic and magnetic properties of double perovskite even though not much variation over their mechanical properties. To illustrate the illumination properties of the compounds under study, the optical properties are also analyzed. Hence this study helps to lead the complete examination of suitable photovoltaic properties of STO and SOTO compounds.

Magnetocaloric Effect, Structural, Magnetic and Electronic Properties of High Entropy Alloys AlCoxCr1−xFeNi: First-Principle Calculations and Monte Carlo Simulations

The magnetocaloric effect, electronic structure and magnetic properties of High Entropy Alloys AlCoxCr[Formula: see text]FeNi ([Formula: see text]) were calculated using the Monte Carlo simulation, the Korringa–Kohn–Rostoker method combined with the coherent potential approximation (KKR-CPA), method of linear augmented plane wave (FPLAPW) within generalized gradient approximation (GGA) and modified Becke–Johnson potential (TB-mBJ). Density of states of AlCoxCr[Formula: see text]FeNi are studied and analyzed. The total magnetic moments of magnetic atoms were calculated and compared with theoretical and experimental results. On the other side, the magnetocaloric effect in AlCoxCr[Formula: see text]FeNi was studied by first-principle calculations (FPCs) and Monte Carlo simulations. The magnetic phase transition temperature is estimated. The Curie temperature and exchange integrals were found to decrease with Co substitution. The magnetic entropy changes and relative cooling power are found.

Stibnite at modified Becke-Johnson exchange potential

The demand for cheaper, nontoxic and earth-abundant materials as absorbing layer for solar cell is immensely needed to replace scarce, toxic and expensive one. In this regard, chalcogenide materials have considerably attracted the attention of a lot of researchers because of showing a great potential for different applications. Stibnite (Sb2S3), a chalcogenide binary material is intensively investigated for exploiting its potential for different energy technologies being a less toxic, abundantly available, stable and efficient one, which are the fundamentals for sustainability as well as to realize the dream of green energy. In this study, a computational study of the structural, electronic and optical properties of the stibnite (Sb2S3) crystal structure is presented using the full potential (FP) linearized augmented plane wave (LAPW) method framed within the density functional theory (DFT). For the estimation of the exchange-correlation potential part, besides the local density approximation (LDA), Wu-Cohen parameterized generalized gradient approximation (WC-GGA) Perdew-Burke-Ernzerhof parameterized generalized gradient approximation (PBE-GGA), and Perdew-Burke-Ernzerhof generalized gradient approximation for solids and surfaces (PBEsol-GGA), the Trans-Blaha approach of the modified Becke-Johnson (TB-mBJ) potential is used to improve the fundamental band gap value. Moreover, these calculations are performed by involving spin-orbit coupling (SOC) contribution as well. Additionally, optical properties, such as imaginary and real parts of the dielectric function, optical conductivity absorption coefficient, refractive index, reflectivity, and electron energy loss function were investigated as well. The obtained results of the band gap energy and optical properties with TB-mBJ potential were found closer to the experimental data and endorse its potentiality for the photovoltaics applications.

Comparative study of optical properties of ZnO Zinc Blend and Rock Salt structures, TB- mBJ and GGA approximations

Currently, the most used transparent conductive oxide (TCO) is the indium tin oxide (ITO). The need for a material that can replace this TCO comes in many studies. Among these materials, we have discussed zinc oxide (ZnO). This work is carried out using full-potential linear augmented plane wave (FP-LAPW) and implemented in the Wien2k. Since the ZnO alloy has different structures, this study aims to discuss the optoelectronic behavior of the F doped ZnO with its different phases and the doping concentration variation where the amount of F is 3.125%, 6.25% and 12.5%. in the visible light range. The comparison between the Rock Salt and Zinc Blend structures gives a starting point to be compared with the third structure which is Wurtzite. TB-mBJ was applied to compare the promising results found by the GGA approximation. Its optoelectronic properties make fluorine-doped ZnO a promising candidate for optoelectronic applications.

Physical characteristics of X2NaMoBr6 (X= K, Rb): A DFT study

The full-potential linearized-augmented plane-wave (FP-LAPW) method based on density functional theory (DFT) was used to investigate the structural, elastic, electronic, optical, magnetic and thermoelectric (TE) characteristics of halide double-perovskites (HDPs) X2NaMoBr6 (X = K, Rb). Perdew, Burke and Ernzerhof generalized-gradient approximation (PBEsol-GGA) + modified Becke-Johnson (mBJ) potential were employed. Enthalpy of formation (ΔH) was found to be −3.243 eV for K2NaMoBr6 and -3.209 for Rb2NaMoBr6 which (negative values) confirm the stability of the compounds. The ferromagnetic behaviour was identified from the integer values of the total magnetic-moment (μB) which were 3.00001 and 3.00002 for K2NaMoBr6 and Rb2NaMoBr6, respectively. Moreover, the value of static dielectric constant ε1(0) was found to be 3.21 for K2NaMoBr6 and 3.27 for Rb2NaMoBr6. TE characteristics were calculated by using Boltztrap code. Both compounds showed the absorption in the UV region (6.86 eV for Rb2NaMoBr6 and 7.11 eV for K2NaMoBr6). Results indicate that both X2NaMoBr6 (X = K, Rb) compounds are appropriate candidates for TE, optical and data storage applications.

Performance Enhancement of APW+lo Calculations by Simplest Separation of Concerns

Full-potential linearized augmented plane wave (LAPW) and APW plus local orbital (APW+lo) codes differ widely in both their user interfaces and in capabilities for calculations and analysis beyond their common central task of all-electron solution of the Kohn–Sham equations. However, that common central task opens a possible route to performance enhancement, namely to offload the basic LAPW/APW+lo algorithms to a library optimized purely for that purpose. To explore that opportunity, we have interfaced the Exciting-Plus (“EP”) LAPW/APW+lo DFT code with the highly optimized SIRIUS multi-functional DFT package. This simplest realization of the separation of concerns approach yields substantial performance over the base EP code via additional task parallelism without significant change in the EP source code or user interface. We provide benchmarks of the interfaced code against the original EP using small bulk systems, and demonstrate performance on a spin-crossover molecule and magnetic molecule that are of size and complexity at the margins of the capability of the EP code itself.

Study of the magnetic properties of LiMn1.5Ni0.5O4 spinel: Ab initio calculation and Monte Carlo simulation

In the present work, the Ab initio calculations, based on Density Functional Theory with the Hubbard correction U (DFT + U) approach and Full potential Linear Augmented Plane Wave (FLAPW) method are used to calculate the exchange integrals for Lithium-Nickel-Manganese Oxide LiMn1.5Ni0.5O4. The exchange integrals values JMn-Mn, JNi-Ni and JMn-Ni are obtained by substituting the totalenergiesof different magneticground states configurationinto theIsing model. Those values are used as input for Monte Carlo simulations to study the magnetization as a function of temperature and external magnetic field for several values of U.

A DFT based analysis of LiYX (X = C, Ge, Si) alloys for energy applications

LiYX (X = C, Ge, Si) half-Heuslar compounds are examined using density functional theory (DFT). WIEN2K kit is used to compute Structural, electronic & optical properties. The full Potential (FP) linearized augmented plane wave (LAPW) technique is used for the calculations. The compounds have optimized lattice parameters in the range 5.7–6.6 Å. The density of states and band structure were also determined and evaluated. The LiYGe and LiYSi alloys have a direct bandgap of 0.68 eV and 0.61 eV at point X, whereas the LiYC compound has an indirect bandgap of 0.48 eV with band transition X → Γ. The optical reflectivity of the alloys is in the ultraviolet region. The high absorption coefficient (>104 cm−1) is obtained. The respective optical conductivity of LiYC, LiYGe, and LiYSi compounds is found to be 7322, 9071, and 8212 in the units of Ohm−1 cm−1 near the UV region. Using real and imaginary parts of the dielectric function, the reflective index, absorption coefficient, electron energy loss, extinction coefficient were also analyzed. Half-Heusler alloys due to their potential applications in solar energy or thermoelectrics are of great interest nowadays. Our results revealed that these compounds are more appropriate candidates for solar and photovoltaic energy applications based on energy bandgap and optical studies. These alloys may act as an alternative to the CdS buffer layer to increase the performance of the device. For experimental fabrications, our computed data may be used as a reference.

Modulating the optoelectronic and thermoelectric properties of chalcopyrite AgXTe2 (X: Ga, In) via in-plane biaxial strain

The influence of biaxial-in-plan strain on optoelectronic and thermoelectric characteristics of AgXTe2 (X: Ga, In) chalcopyrite type compound has been investigated using density function theory base on full potential linear augmented plane wave technique. The generalized Perdew-Burke-Ernzerhof gradient approximation (PBEsol GGA) is used to optimize unit cell and the Tran-Blaha modified Becke-Johnson (TB-mBJ) approach is employed to improve the electronic, optical and thermoelectric properties. The effects of biaxial strains of the tensile (1%, 2%, 3%) and compression (-1%, -2%, -3%) have been calculated along with contribution of two cations (Ga and In). The calculated band gap of AgGaTe2 and AgInTe2 without strain is 1.17 and 1.13 eV that decreases with applied tensile strain and increases with compressive strain. Without strain maximum absorption is obtained at 1.3 eV and 1.1 eV AgGaTe2 and AgInTe2 respectively, however, tensile and compressive strain shows red and blue shift accordingly. The increase in flatness of valance band with compressive strain results in a large Seebeck coefficient due the large hole effective mass. This identifies AgGaTe2 as a possible efficient thermoelectric material. Consequently, the present study is very useful for developments of desired characteristics by applying strain for optoelectronic and thermoelectric devices.

Stress tensor in the linearized augmented plane wave method

In this paper we present a detailed derivation of the stress tensor for the nonrelativistic full potential linearized augmented plane wave (LAPW) method. The formalism has been implemented into the wien2k code and has been thoroughly tested for the equilibrium lattice parameters in various solids. Hydrostatic and nonhydrostatic conditions have been applied and the accuracy of individual stress components has been tested at finite strain. We also tested the convergence of the stress tensor with respect to the basis set and found it necessary to increase the basis set a bit as compared to total energy calculations. The effect of the tetrahedron and Fermi-Dirac (FD) methods on the calculated stress is studied for aluminum and found that the FD method improves the results. Finally, a brief comparison with previous attempts in the literature on this topic is given.

Structural, electronic and magnetocaloric properties of antiskyrmion hosting Heusler compounds: Mn2PtSn and Mn1.4PtSn

In this work, we have studied the structure, electronic and magnetic properties of Mn2PtSn and Mn1.4PtSn by using the ab initio calculations and Monte Carlo study. The ab initio calculations, based on the functional theory of density combined with the method of linear augmented plane waves at potential, are performed to investigate both electronic and magnetic properties of the two compounds. The total and partial densities of two systems have been calculated. Mn1.4PtSn, the first known Heusler tetragonal (Mn vacancy-induced) superstructure compound, opens a new direction of research for superstructure-related properties in a family containing multiple compounds. We have deduced the total magnetic moment of the two systems. We observe an anisotropic fractal magnetic pattern of zero-field closing domains above the spin-reorientation transition temperature, which transforms into a set of high-field bubble domains. Below the spin-reorientation transition temperature, the strong in-plane anisotropy as well as the zero-field fractal self-affinity is gradually lost, while the formation of high-field bubble domains remains robust. The magnetization, specific heat and magnetic entropy change have been obtained by using the Monte Carlo simulations. The relative cooling power has been obtained for different values of external magnetic field and temperatures.

Structural, Electronic, Magnetic and Mechanical Properties and Magnetocaloric Effect of the Full-Heusler Co2MnGa

Structural, electronic, magnetic and mechanical properties of the Co2MnGa have been calculated with functional density theory using full potential linear augmented plane wave method as implemented in the Wien2k code. Exchange correlation effects for these properties are treated by generalized gradient approximation while for electronic and magnetic properties, in addition to (WC-GGA) correction, mBJ-GGA scheme was also applied. The stiffness constant of the spin wave and the Curie temperature are calculated. Moreover, mechanical parameters included three elastic constants, compression modulus, Young’s modulus and shear modulus are also investigated. This theoretical study provides detailed information on the compound Co2MnGa, in different aspects and can also provide information on the application of this material. Obtained data from ab initio calculations are used as input for Monte Carlo simulations to study the magnetic properties and magnetocaloric effect. Transition temperature, magnetic entropy change, adiabatic temperature change and relative cooling power were found.

Intrinsic ferromagnetism in CoBr2 nanolayers: a DFT + U and Monte Carlo study

The intrinsic ferromagnetism of CoBr2 bulk was investigated using DFT (density functional theory) combined with the full potential linear augmented plane wave method and Monte Carlo simulations. The ground state of CoBr2 exhibits ferromagnetic behavior and a semiconductor character. We used the generalized gradient approximation (GGA) and GGA + U (Hubbard correction) approximations to determinate the magnetic moment. The magnetic moment reached the experimental value and was in good agreement with the other theoretical values. The value obtained was used as an input to a Monte Carlo study to calculate the thermal magnetization and magnetic hysteresis cycles. Ferromagnetic behavior was observed and was found to be due to an positive exchange interaction. These results lead us to believe that this material could be a promising spintronic material.

Magnetic properties and half metallic behavior of the Full-Heusler Co2FeGe alloy: DFT and Monte Carlo studies

The study of structural, electronic and magnetic alloy properties of the full-Heusler Co2FeGe has been undertaken using the first principle method based on the density functional theory (DFT). In this work, we have predicted and underlined the mechanism of the half-metallic behavior of the full-Heusler Co2FeGe alloys by using the Monte Carlo simulations. We have used the full potential linear augmented plane wave (FPLAPW) method as implemented in the Wien2K code to forecast the electronic and magnetic properties of the studied system. We have used the generalized gradient approximation GGA for the treatment of exchange energy and correlation. We have also taken into account the strong correlations orbital of Co and Fe atoms by applying the GGA ​+ ​U approximation founded on DFT ​+ ​U. The GGA ​+ ​U gives a good result showing that compound Co2FeGe is a half-metallic ferromagnetic (HMF) through a large gap of 1.20 ​eV. The value of the magnetic moment is used as input to calculate the magnetic parameter of this alloy when using the Monte Carlo simulations. By the help of the proposed model the temperature dependency of the magnetization, the susceptibility and the specific heat, is studied. The phase transition is of second order type at the critical temperature point. This temperature is in good agreement with the available experimental data.