Full-potential Augmented Plane Wave Research Articles

Electronic structure and thermoelectric properties of orthorhombic spinel-derived AgInSnS4 compound: First-principles investigation

The electronic structure and thermoelectric properties of the orthorhombic spinel-derived AgInSnS4 compound were investigated using the Linearized Full-Potential Augmented Plane Wave Method (FP-LAPW), which is fundamentally based on density functional theory (DFT), in combination with semi-classical Boltzmann transport theory. According to the electronic band structure calculation, the AgInSnS4 compound is a semiconductor with a fundamentally reduced indirect bandgap of about 0.50 eV and 1.27 eV obtained within the GGA-PBE and TB-mBJ approaches, respectively. Moreover, the evaluation of the thermoelectric properties shows that the AgInSnS4 compound has a large Seebeck coefficient combined with high electrical conductivity, resulting in a high figure of merit (ZT) value of 0.81 at high temperature, making it a suitable candidate for thermoelectric applications.

Investigation of structural, electronic and lattice dynamical properties of YMgNi4H4 cubic and orthorhombic for hydrogen storage applications

This work presents the results obtained from ab initio calculations based on Density Functional Theory (DFT), to study the compound YMgNi4H4 in two phases cubic and orthorhombic, two methods were used: Full Potential Linearize Augmented Plane Waves (FP-LAPW) and Plane Waves Pseudo Potential (PW-PP). The obtained structural properties agree well with previous works. The cohesive energy, hydrating enthalpy and the formation enthalpy are negative for both structures, our results predict that the orthorhombic phase is the most stable. The calculated band structure indicates that this material has metallic behavior. The elastic constants were calculated using the Density Functional Perturbation Theory (DFPT) formalism. The two structures are mechanically stable based on their values, and other mechanical properties such as the bulk modulus, Young's modulus, shear modulus, Poisson's coefficient were calculated using these elastic constants. By analyzing the elastic anisotropy, this material has a pronounced anisotropy. Using the DFPT, the dispersion of the phonons has been calculated for the two phases, it indicates the stability of these two phases because we notice the absence of imaginary modes. Finally, in the [0, 1540] K° range, the variations of thermodynamic properties as a function of temperature were measured.

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.

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.

Theoretical study of the structural, electronic and magnetic properties of film surface and bulk based quaternary Heusler alloys Ni-Co-Mn-In

In this work, we will the theoretical study of the electronic and magnetic properties of thin (001) surface layers of about 1μm in size based on Heusler Ni50Mn34.5In15.5 quaternary alloys developed on monocrystalline MgO substrates (001) at low temperature. We will use in this study some approximations depending on the density functional theory. Additionally, we will use the Linearized Full Potential Augmented Plane Wave (FP-LAPW) method to calculate these properties. The theoretical results are given by the generalized gradient approximation. The total and partial moments and gap energy of NiCoMnIn bulk and Ni50Mn34.5In15.5 film were calculated. The two systems represent a half-metal character.

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.

A DFT investigation of CsMgX3 (X = Cl, Br) halide perovskites: Electronic, thermoelectric and optical properties

The electronic, thermoelectric and optical properties of cubic CsMgX3 (X = Cl, Br) are performed using full potential augmented plane wave (FP-LAPW) method with the generalized gradient approximation (GGA) and modified Becke-Johnson (mBJ-GGA) approximation as exchange correlation potentials. The band profile of CsMgCl3 and CsMgBr3 using mBJ-GGA potentials exhibits indirect wide energy band gap of 6.35 and 4.26 eV, respectively. Further, thermoelectric properties are carried out as a function of temperature (100–1200 K) and chemical potential using BoltzTrap code. It has been found that thermoelectric efficiency increases with increasing temperature upto 1200 K. The figure of merit (ZT) values are calculated to 0.69 and 0.75 at room temperature for CsMgCl3 and CsMgBr3, respectively. Furthermore, optical properties are computed in the energy spectrum (0–12 eV). These materials absorb light in ultra violet region and can be used as absorber of UV-rays. Also materials are suitable for thermoelectric power generator applications.

Exploration of New Double Peroviskites Cs2YInX6 (X = Cl, Br, I) for Opto-Electronic and Sustainable Energy Applications

We used theoretical and computational methods to explore the double perovskites Cs2YInX6 (X = Cl, Br, I) by having the scope and goal of finding their physical aspects and characteristic. To properly explain different phenomenological features of density functional theory (DFT), the ab-initio computational model based on the approximation of full-potential augmented plane wave plus local orbitals (FP-LAPW + lo) technique was implemented. The calculated ground state properties with GGA-PBEsol agree well with the available other theoretical data. Mechanical properties, another very important aspect of these double perovskites, are found by using shear modulus, Young’s modulus, and Poisson’s ratio. Further, we obtained bandgaps by investigating electronic properties with and without spin–orbit coupling (SOC). In order to calculate and compare the bandgaps with experimental results, we used SOC in connection with mBJ potential to investigate the direct bandgaps of Cs2YInCl6 (Eg = 0.45 eV), Cs2YInBr6 (Eg = 0.65 eV) and Cs2YInI6 (Eg = 0.82 eV) respectively. Furthermore, optical properties are investigated in terms of calculations like complex dielectric constants (ε(ω)), refractive index (n(ω)), reflectivity (R(ω)) and absorption co-efficient (α(ω)) to find their possible applications in optoelectronic devices. In view of this background, BoltzTraP code will also be used to explore these double perovskites in respect of their thermoelectric applications.

Ab initio DFT determination of structural, mechanical, optoelectronic, thermoelectric and thermodynamic properties of RbGeI3 inorganic perovskite for different exchange-correlation functionals

As a potential counterpart to the toxic CH3NH3PbI3 for photovoltaic applications, a lead-free non-toxic perovskite, rubidium germanium iodide (RbGeI3) is analyzed to assess its structural, mechanical, elastic, optoelectronic, thermoelectric and thermodynamic properties using the Full-Potential Augmented Plane Wave (FP-LAPW) approach of the WIEN2k code using density functional theory. Though various exchange correlation functionals viz. the Perdew Burke Ernzerhof scheme of Generalized Gradient Approximation (PBE-GGA), PBEsol, and WC-GGA are used, the TB-mBJ exchange correlation potential coupled with GGA, provides enhanced results. The lattice constants a0, bulk modulus B and its pressure derivative Bp are estimated to be 11.619096 bohr, 19.34 GPa and 5.4303 respectively with TB-mBJ exchange correlation potential. The elastic constants, C11, C12 and C44, Young’s modulus E, Shear modulus G, Poisson’s ratio ν and Anisotropic ratio A are estimated to be 43.4 GPa, 7.3 GPa, 7.9 GPa, 27.93 GPa, 11.09 GPa, 0.26 and 0.07 respectively using the Elastic 1.0 package. The density of states (DOS) and band structure are plotted for various exchange correlation functionals. The energy band gap and the absorption coefficient of the material, 1.338 eV and 10−3 cm−1 respectively, are found to be suitable for photovoltaic applications. Various thermoelectric coefficients like Seebeck coefficient, electrical conductivity and thermal conductivity are also calculated. The thermodynamic properties like Debye temperature, heat capacity, entropy and thermal expansion coefficient are plotted as a function of temperature and pressure using Gibbs2 program. The study indicates that inorganic cubic RbGeI3 has all the characteristics required as an absorber material for perovskite solar cells. However, the phonon dispersion spectrum shows the presence of imaginary modes indicating an instability in the structure with rise in temperature.

Electronic and optical properties of Fe doped GaN graphene based: Using DFT

The electronic and optical properties of GaN graphene-based in the pure case and Fe doped at two different positions have been calculated using a density functional theory framework with full potential augmented plane waves plus local orbitals. The GaN sheet is a non-magnetic semiconductor doping Fe to the N (N-site) and Ga (Ga-site) sites has caused the half-metallic and magnetic semiconductors, as seen in the p-type and n-type treatment in the up and down spins for the last case. The optical curves include the real and imaginary parts of the dielectric function, ELF, Reflection, and absorption indexes in the presence of the Fe doped for the N- and Ga-sites were calculated along the x (E||x) and z (E||z) directions. The N-site case's metallic behavior in the infrared (IR) area is too large for the E||x direction and has spontaneous emission. The Ga-site one has the semiconductor behavior along x and z directions by 0.7 eV and 4 eV gaps.

The effect of Fe impurity on electronic and optical properties of graphene-like InAs: a DFT-based study

The first-principles calculations have been applied to investigate the impact of Fe impurity on the electronic, magnetic, and optical properties of graphene-like InAs and compare the results. The calculations have been accomplished through the full-potential augmented plane wave technique in the density functional theory framework using WIEN2k computational software. The band structures, density of states, and magnetic moment have been calculated. Since the presence of Fe causes magnetic effects such as spin–orbit interaction and electronic treatment variations, substituting In by Fe changes the non-magnetic InAs nanosheets semiconductor to a metalloid with the magnetic moment of about 5 Bohr magneton. Moreover, both real and imaginary diagrams of the dielectric function, loss function, optical conductivity, refraction index, and extinction coefficients have been discussed in the pure and impure cases.

Electronic band profiles, magnetic stability, antiferromagnetic spins ordering and thermodynamics properties of novel antiferromagnet CaCr2Sb2

We have analyzed the magnetic stability; antiferromagnetic spin ordering; electronic, magnetic and thermodynamic properties of CaCr2 Sb2 compound using the framework of density functional theory (DFT) with full-potential augmented-plane wave (FP-APW) method within the generalized gradient (PBE-GGA, Tran-Blaha modifies GGA) plus Hubbard potential U (GGA + U ) functional as exchange correlation potentials. We have clearly specified that the antiferromagnetic state is most favorable for CaCr2 Sb2 as compared to other configurations at their structural relaxed lattice parameters. In antiferromagnetic (AFM ) spin configuration, a Cr atom is shown to be in an impressive state of CaCr2 Sb2 compound. Based on its band structures and density of state (DOS), CaCr2 Sb2 has a metallic character in paramagnetic (PM ) and antiferromagnetic phase (AFM ). From projected densities of states, it is considered that the primarily bonding is achieved throughout hybridization of Cr (3d) with Sb (p ) states. Moreover, pressure and temperature contingent thermodynamic parameters are calculated in the range of 0 to 1000 K and 0 to 18 GPa for temperature and pressure, respectively, with a step range of 3 GPa, respectively. The total magnetic moment of CaCr2 Sb2 is confirmed to be 0.00008/4.07 μ B in the antiferromagnetic/ferromagnetic configuration respectively using GGA + U where its major contribution originates from Cr atoms.

Prediction of the Half Metallicity in Ferromagnetic Germanium Telluride (GeTe) Doped with Titanium

This research work studies the structural, electronic and magnetic properties of Ge[Formula: see text]TixTe (for [Formula: see text], 0.50, 0.75, 1) compounds in rock-salt structure based on first-principles spin-polarized density functional theory. As it is implemented in WIEN2k code, the full-potential augmented plane-wave method was used in the investigation. To evaluate the structural properties of compounds, the exchange-correlation term is estimated using PBE-GGA approximation. For the other properties such as the electronic structures, densities of states and local moments, the generalized gradient approximation PBE-[Formula: see text] is used. The analysis of spin-polarized density of states has shown the half-metallic ferromagnetic character when [Formula: see text] and 0.75; while at [Formula: see text], we obtained near half-metallic behavior. In order to validate the effects resulting from exchange splitting process, we calculated the exchange constants [Formula: see text] and [Formula: see text]. For Ti atomics sites, the value of total magnetic moment has been estimated equal to [Formula: see text] in all studied compounds. We have found that the local magnetic moment of Ti is reduced and small local magnetic moments on nonmagnetic atomics sites of Ge and Te were created by the p-d hybridization effect.

Investigation of the structural, electronic, optical, elastic, and thermodynamic properties of the zinc blende Ga1-xAlxAs1-yPy quaternary alloys: A DFT-Based simulation

In this work, the effect of the composition on the structural, electronic, elastic, optical and thermodynamic properties of the Ga1-xAlxAs1-yPy quaternary alloys are investigated using the full-potential augmented plane wave plus local orbitals (FP-APW + lo) approach in the density functional theory framework as embodied in the WIEN2k computational package. The fundamental physical properties of the cubic Ga1-xAlxAs1-yPy quaternary alloys, such as lattice constant, bulk modulus, energy band structure and elastic constants, are predicted for the first time. The obtained results show that the Ga1-xAlxAs1-yPy quaternary alloys are direct band gap semiconductors, while their parents; GaP, AlAs, and AlP binary compounds are indirect band gap semiconductors. It is found that the studied materials are of brittle character and ionic bonding nature. The static dielectric constant and static refractive index of the considered alloys are calculated and compared with the obtained results using empirical models. Pressure and temperature dependencies of some thermodynamic parameters of the title quaternary alloys are also investigated and discussed.

Orthorhombic phases in bulk pure HfO2: Experimental observation from perturbed angular correlation spectroscopy

In pure HfO2, only P21/c monoclinic phase was known to exist from previous investigations and there is no report of orthorhombic phase in pure bulk HfO2 at ambient temperature and pressure. Present atomic scale measurements by perturbed angular correlation (PAC) spectroscopy, report two orthorhombic phases in pure bulk HfO2 at room temperature along with the most commonly observed monoclinic phase (∼80%). By comparing with the calculated results of density functional theory using full potential (linearized) augmented plane wave method (FP-LAPW), these two orthorhombic phases have been attributed to structures with space group Pbca and Pca21. The structures with space group Pca21 and Pmn21 are non-centrosymmetric and were found to be responsible for ferroelectricity in doped thin film HfO2. At room temperature, the site percentages for the Pca21 and Pbca have been found to be ∼6% and ∼10%, respectively. At high temperatures of 973 and 1073 K, the Pca21 phase was not found but, the Pbca orthorhombic phase was found to be present in the whole temperature range from 298 to 1073 K. The third orthorhombic phase Pmn21 was not observed in bulk HfO2. Interestingly, In Gd doped (5 at%) HfO2, these two orthorhombic phases enhance more than the monoclinic phase. In Gd doped oxide, the P21/c monoclinic phase reduces to ∼24% while the site percentages for the two orthorhombic phases have been found to be ∼54% (Pbca) and ∼17% (Pca21).

Optical and electronic properties of zigzag boron nitride nanotube (6,0): DFT study

The optical and electronic properties of boron nitride nanotubes have been studied using the full potential linear augmented plane wave method in the framework of density functional theory. The electronic properties such as band structure and density of states have been investigated using the generalized gradient approximation. In addition, the optical parameters of boron nitride nanotube (6,0) have been investigated such as real and imaginary parts of the dielectric function, electron energy loss function, refractive index, extinction coefficient, and optical conductivity. The obtained values are in better agreement with the available experimental data.

Pressure Effect Study on the Electronic and Optical Properties of BxIn1 – xAs Alloys Using DFT Calculation

In order to extract structural and electronic properties of BxIn1 – xAs ternary alloys and enrich the database of materials based on boron and indium, we have used full-potential augmented plane wave (FP-LAPW) method through the density function theory (DFT) and within generalized gradient approximation (GGA), local density approximation (LDA), and Tran–Blaha modified Becke–Johnson approximation (TB–mBJ). We have optimized the cohesive energy of our binary compound and ternary alloys versus volume of the unit cell firstly, and we have found that the optimum volume, lattice parameter, and the bulk modulus vary for different boron concentrations. Using DFT–mBJ calculations, we found that InAs possess direct band-gap energy and an indirect gap semiconductor for BAs and B0.75In0.25As. However, B0.25In0.75As and B0.5In0.5As ternary alloys have a metallic and semi metallic characters, respectively. We also studied the optical properties of our BAs and InAs binary and B0.75In0.25As ternary semiconductors and their behaviors are also investigated under the application of hydrostatic pressure in a range of 0 to 25 GPa. In summary, we conclude that the incorporation of boron atom in InAs increase its hardness and affects the band-gap energy considerably, and therefore provides a novel research perspective. We note that InAs binary compound loses its semiconductor character and becomes semi-metal at 5 GPa.

High-pressure induced magnetic phase transition in half-metallic KBeO3 perovskite

In this paper, we present the study of the structural, mechanical, magneto-electronic and thermodynamic properties of the perovskite KBeO3. The calculations were performed by the full potential augmented plane wave method, implemented in the WIEN2k code which is based on density functional theory, using generalized gradient approximation. The computed formation energy and elastic constants indicate the synthesizability and mechanical stability of KBeO3. Moreover, our results showed that the latter is a half-metallic material with half-metallic gap of 0.67 eV and an integer magnetic moment of 3μB per unit cell. In addition, KBeO3 maintains the half-metallic character under the pressure up to about 97 GPa corresponding to the predicted magnetic-phase transition pressure from ferromagnetic to non-magnetic state. The volume ratio V/V0, bulk modulus, heat capacity, thermal expansion and the Debye temperature are analyzed using the quasi-harmonic Debye model.

Uniaxial Strain and Optical properties of GaP Nanowires

The optical properties for wurtzite (WZ) Bulk GaP and GaP nanowires (GaP-NWs) in hexagonal(circular), triangular and square cross sectional are investigated by using full potential linear augmented plane waves and local orbitals (FP-LAPW-LO) method based on density functional theory (DFT). The wurtzite nanowires are investigated with diameters limited to ~27 oA. The optical functions as a function of photon energy have been investigated for unstrained bulk WZ-GaP and WZ-GaP-NWs in the first part. Finally, the optical functions are investigated for WZ-GaP-NWs by applying uniaxial strain from -5% to +5%. The effect of cross sectional variation in the area and shape of the NWs on the optical functions is clear when compared with bulk GaP. GaP-NWs kept real dielectric constant positive and refractive index close to vacuum value for a wider range of energy on the contrary of bulk GaP. It is found that the dielectric constants are slightly increased from the unstrained GaP-NWs values with strain increases. A shift in the threshold energy for toward higher energy as the strain changes from tensile to compressive. The refractive index shows a small change when passing from compressive toward tensile strain. It is found that GaP-NWs could play a role in solar cells structure and high speed electronic circuits.

Uniaxial Strain and Optical properties of GaP Nanowires

The optical properties for wurtzite (WZ) Bulk GaP and GaP nanowires (GaP-NWs) in hexagonal(circular), triangular and square cross sectional are investigated by using full potential linear augmented plane waves and local orbitals (FP-LAPW-LO) method based on density functional theory (DFT). The wurtzite nanowires are investigated with diameters limited to ~27 oA. The optical functions as a function of photon energy have been investigated for unstrained bulk WZ-GaP and WZ-GaP-NWs in the first part. Finally, the optical functions are investigated for WZ-GaP-NWs by applying uniaxial strain from -5% to +5%. The effect of cross sectional variation in the area and shape of the NWs on the optical functions is clear when compared with bulk GaP. GaP-NWs kept real dielectric constant positive and refractive index close to vacuum value for a wider range of energy on the contrary of bulk GaP. It is found that the dielectric constants are slightly increased from the unstrained GaP-NWs values with strain increases. A shift in the threshold energy for toward higher energy as the strain changes from tensile to compressive. The refractive index shows a small change when passing from compressive toward tensile strain. It is found that GaP-NWs could play a role in solar cells structure and high speed electronic circuits.