FP-LAPW Method Research Articles

The first principle calculations of structural, magneto-electronic, elastic, mechanical, and thermoelectric properties of half-metallic double perovskite oxide Sr2TiCoO6

The structural, elastic, mechanical, magneto-electronic, and thermoelectric properties of Sr2TiCoO6 double perovskite oxide have been studied within the framework of density functional theory. The FP-LAPW method within the (GGA) and (mBJ) approximations is chosen in the computational approach. This alloy crystallizes in cubic structure with the ferromagnetic phase. The computed lattice constant was found to agree with the available experimental results. This compound shows the half-metallic ferromagnetic properties. A value of 1 µB is found for the total magnetic moment with an important contribution from Co atoms. The elastic parameters reveal that Sr2TiCoO6 as being super hard and brittle. We calculated the thermoelectric properties of Sr2TiCoO6 using the Boltzmann transport equations within the DFT in a temperature range from 100 to 1000 K. The transport parameters like Seebeck coefficient, electrical thermal conductivity and the merit factor, have been put together to establish their thermoelectric response. The figure of merit value is between [0.71-0.99] indicating that our compound is a good candidate for thermoelectric applications at high and low temperatures.

Structural, electronic, and optical properties of the gallium nitride semiconductor by means of the FP-LAPW method.

In the present paper, the structural, electronic, and linear optical properties of different phases of the gallium nitride (GaN) have been investigated. The zinc blende and wurtzite phases of the GaN have been studied using the full-potential linearized augmented plane wave method (FP-LAPW). In our study, many approximations have been used, such as the local density approximation (LDA), the generalized gradient approximation (GGA), the Engel and Vosko generalized gradient approximation (EV-GGA), and the modified Becke-Johnson (mBJ) potential exchange. As a result, we found a very good agreement with literature experimental results for the energy band gap using the mBJ approximation with a scaling factor of 98% and 80% for the zinc blende and wurtzite phases, respectively.

Ab initio studies of structural, electronic and magnetic properties of Al1-xMnxN in zinc blende structure

First-principles method has been applied to calculate the structural, electronic and magnetic properties of the Al1-xMnxN alloys (with x = 0.0, 0.125, 0.25, 0.375, 0.50, 0.625, 0.75, 0.875 and 1.00) in the zinc blende structure (ZB), using FP-LAPW method within the spin-polarized density functional theory. We have studied the band structure and magnetic moment as a function of the lattice parameter of the MnN compound and the ternary alloys Al1-xMnxN. The magnetization increases as the lattice parameter increases and tends to saturate at the value 4μB for MnN and 8 μB for the ternary alloys. We also found that the ternary alloys with x = 0.125 and 0.25 are ferromagnetic in nature and candidate to be half-metallic material; the majority spin states show metallic behavior and the minority spin states show semiconducting behavior. The three concentrations x = 0.375, 0.5 and 0.625 are founded to be semi-metals within the PBE-GGA approach, while they are half metals within the modified Becke-Johnson (mBJ-GGA) approach.The remaining concentrations are found to be semi-metals. It was found that the lattice parameter and the total magnetic moment strongly depend on the Manganese (Mn) concentration.

Ab Initio Investigations of the Structural, Electronic, Magnetic, and Thermal Properties of Cr2TaGe1-xSnx Quaternary Heusler Alloys

The first-principle calculations were performed in the framework of the density functional theory (DFT) using FP-LAPW method as implemented in Wien2k code to determine the structural stability, electronic, and magnetic properties of quaternary Heusler alloys Cr2TaGe1-xSnx (x = 0, 0.25, 0.50, 0.75, 1.00), The results showed that for the compounds, the AlCu2Mnl-type structure is energetically more stable than CuHg2Ti-type structure at the equilibrium volume. The calculated lattice constants for Cr2TaGe and Cr2TaSn are 6.081 A and 6.311 A, respectively. For mechanical properties, shear modulus, Young’s modulus, elastic constants, Poisson’s ratio and shear anisotropy factor have studied. Their obtained values reveal that these compounds are mechanically stable. The electronic band structures and density of states of our compounds show a half metallic character with total magnetic moments, − 3.00 μB per formula unit with indirect band gap, 0.569 eV and 0.482 eV for Cr2TaGe and Cr2TaSn respectively. Regarding thermal properties such as the thermal expansion coefficient, heat capacity, and Debye temperature, we have applied a very suitable model for studying thermodynamics quantities called the quasi-harmonic Debye model. On the basis of these results, these alloys are predicted to be good candidates for future spintronic applications.

Effect of a small Mn and Sr deficiency on the physical properties of SrMnSb2

Nonstoichiometric Sr1-yMn1-zSb2 (y ∼0.07, z ∼0.02) and its pure compound SrMnSb2 were suggested to be magnetic topological semimetals. First-principles calculations using the FP-LAPW method by means of generalized gradient approximation (GGA) have been used to investigate the structural, electronic, magnetic, thermodynamic, and thermoelectric properties of SrMnSb2, and Sr1-yMn1-zSb2 compounds in a temperature range from 0 K to 800 K. Our results show that small reduction of Sr and Mn atoms leads to an interesting change in their physical properties. The thermodynamic and magnetic study show that the Sr1-yMn1-zSb2 compound exhibits considerable thermal and magnetic behavior, while SrMnSb2 compound reveals highest transport effects.

Study of the impact due to spin-orbit coupling effect on the optical properties of InP1−xSbx alloys in mid-infrared applications: A DFT approach

The optical properties of InP1−xSbx(at, x = 0.25, 0.50 and 0.75) supercell structure have been computed utilizing TB-mBJ scheme under FP-LAPW method employing WIEN2K package. The study of optical properties for the supercell structures includes the analysis of absorption, reflection, refraction and energy losses characteristics with increasing incident photon energy. This study also claims the non-negligible impact of SOC (Spin-orbit Coupling) effect in the supercell structures due to enhanced Sb incorporation. The refractive index and extinction coefficient values are obtained to be significantly higher for the supercell structures. A resemblance between real (imaginary) part of the complex dielectric constant with complex refractive index has been interestingly observed. An enhanced smoothness of the absorption characteristics curve along with distinct peak values occurs due to the impact of SOC effect in the supercell structures with increased Sb incorporation. The presence of SOC effect led to obtain significant higher values of optical conductivity and reflection coefficient, thereby signifying the material to be lossy in nature. The occurrence of distinct plasma frequency peaks has been observed in the supercell structures due to an enhanced degree of SOC effect. Most interestingly, with increase in Sb incorporation in the supercell structures, a blue shift has been observed in each of the optical characteristic curves.

Robust mixing in self-consistent linearized augmented planewave calculations

We devise a mixing algorithm for full-potential (FP) all-electron calculations in the linearized augmented planewave (LAPW) method. Pulay’s direct inversion in the iterative subspace is complemented with the Kerker preconditioner and further improvements to achieve smooth convergence, avoiding charge sloshing and noise in the exchange–correlation potential. As the Kerker preconditioner was originally designed for the planewave basis, we have adapted it to the FP-LAPW method and implemented in the exciting code. Applications to the 2 × 2 Au(111) surface with a vacancy and to the Pd(111) surface demonstrate that this approach and our implementation work reliably with both density and potential mixing.

Thermoelectric and optical properties of the SrS graphene by DFT

ABSTRACT The mechanical, electrical, optical and thermoelectric properties of SrS graphene-like structure are discussed using the density functional theory and FP-Lapw method. To calculate the electrical properties, the generalized gradient approximation, Kohn–Sham, and Green function Waves function approximations are used in our correlation potential, and the optical calculations are performed based on the Time-dependent density functional theory (TDDFT), Bethe-Salpeter equation, and Random Phase approximation approximations. The structural calculations suggest the phonon stability of SrS, with an observed optical phonon gap in the range of 5–9 THz, indicating that the bonds are ionic. The electronic calculations show that the SrS graphene-like has a direct bandgap of 2.6 eV and also the static value of its real dielectric function has the maximum value with RPA, and minimum value with BSE approximations. In the BSE and TDDFT approximations, the optical behaviour of SrS graphene-like shows optical stability in the infrared, visible and UV edge regions. It has an excellent thermoelectric quality at room temperature, and remarkably its thermoelectric behaviour is stable even beyond 500 K, hence it is a good choice for power generators.

Ab-initio investigation of optoelectronic and thermoelectric properties in new p-type Rattling Heuslers Sr2PtX (X=Se and Te)

The structural, optoelectronic, and thermoelectric properties of the cubic Rattling Heusler compounds Sr2PtX (where X = Se, Te) are evaluated using the FP-LAPW method based on DFT within modified Becke-Johnson potential functional. The BoltzTraP code is used to calculate the thermoelectric properties. PBE-GGA calculations show that Sr2PtSe and Sr2PtTe are semiconductors with indirect band gaps estimated at 0.96 and 0.81 eV, respectively, while corresponding TB-mBJ calculated values are 1.45 and 1.33 eV. High figures of merit calculated at 1200 K (0.65 for Sr2PtSe and 0.38 for Sr2PtTe) and ultralow thermal conductivity indicate that the compounds investigated are good thermoelectric materials.

A combined density functional (PBE, WC and Tb-mBJ) study about the optoelectronic properties of copper-rich ternary chalcogenide materials

Here, we thoroughly studied the ground state structural, electronic and optical properties of high crystalline type cubic ACu3Se4 (A = Ta, Nb and V) ternary chalcogenide materials. The the FP-LAPW method within the framework of density functional theory is employed. The electronic structure calculations are treated with highly accurate modified-Becke-Johnson potential to yield the exact band gap values along with the use of Perdew-Burke-Ernzerhof and Wu-Cohen generalized gradient approximation approach for the corresponding optical properties. The band structures and density of states for the three materials are compared and discussed in detail. The complex optical dielectric function’s and the related optical parameters like the absorption coefficient, reflectivity, energy loss function refractive indices and extension coefficient were calculated and discussed in detail for radiations up to energy value of 14 eV. The calculated optical properties display a significant anisotropy between the two components. We further studied the inter-band contributions for the optical characteristics in these ternary chalcogenides. Our described results could pave the way towards further fundamental investigations of the optoelectronic properties of these direct band gap semiconductors in nanoscale regime for solar energy harvesting.

The Origin of Half-Metallicity in SrO Doped with Transition Metal Atoms Silver and Gold: a First Principles Calculations

In this GGA study, electronic and magnetic properties were investigated with the implementation of the FP-LAPW method within the framework of DFT. Resulting compounds Ag0.125Sr0.875O and Au0.125Sr0.875O were formed by substituting transition metal atoms silver and gold in strontium oxide with 12.5% concentration. Formation energy values show the compounds are stable in the ground state. Volume optimization curves predict the doped compounds are stable in the ferromagnetic phase. Total DOS and band structure plots display half-metallicity at the Fermi level, and also magnetic moment was found in the supercells.

First principle studies of rubidium lead halides towards photovoltaic application

All inorganic perovskites have attracted enormous attention of late owing to their outstanding applications in photovoltaic area including highly stable perovskite solar cells. In-depth understanding of the optoelectronic and transport properties of such materials are vital for practical implementation of the same. The carrier transport properties of the electronic devices based on perovskite materials significantly depend on the effective mass of the respective charge carriers. Here, we have performed first principle calculations with FP-LAPW method for the orthorhombic rubidium lead halides (RbPbX3, where X = I, Br, Cl) to study the optoelectronic and transport properties. The reduced effective mass is found to be minimum for RbPbI3, suggesting an efficient charge carrier transport in the corresponding material. Our calculated values such as the dielectric constants, refractive indices, absorption coefficients and reflectivities show good agreement with reported experimental data. Excitons for RbPbI3 and RbPbBr3 are of Mott–Wannier type while it is of Frenkel type for RbPbCl3. Moreover, estimated band edges of RbPbI3 show a favorable charge carrier transport when it is used with TiO2. Spectroscopic limited maximum efficiency (SLME) of 11.59% can be achieved for 500 nm thick single junction solar cell of RbPbI3.

Electronic, optical and magnetic properties of low concentration Ni-doped CdSe by first principle method

The electronic, magnetic and optical properties of Ni-doped CdSe diluted magnetic semiconductors have been explored by density functional theory-based FPLAPW method as incorporated in the Wien2k code. The band structure and density of states analysis for up spin channel and down spin channel illustrate half-metallic ferromagnetic behaviour. The calculated values of the band gap in an insulating channel (down spin channel) increases from 0.4 to 0.8 eV with increasing the doping concentration of Ni from 6.25 to 25%. The magnetic moment of Ni decreases and magnetic moment on nonmagnetic side increases, which shows the strong pd-hybridization. Furthermore, the optical properties are characterized in terms of dielectric constants, refractive index, extinction coefficient, absorption coefficient and optical loss factor. The static values of the dielectric constant and refractive index are consistent with each other.

Study of the structural, mechanical and thermodynamic properties of the new MAX phase compounds (Zr1-xTix)3AlC2

The structural, electronic, mechanical and the thermodynamic properties of the MAX phases (Zr1-xTix)3AlC2 compounds have been investigated by using the full-potential plane-wave FP-LAPW method as implemented in the Wien2k code. The exchange-correlation (XC) energy of electrons was treated using the Perdew–Burke–Ernzerhof parametrization. The ground-state properties for the studied compounds were calculated and compared with available experimental and theoretical data. The calculated lattice parameters are reasonably comparable with experimental and theoretical results. The formation energy has been evaluated in order to determinate the stability of our compounds. The calculation of the electronic structure was predicted for the first time for the present MAX phase compounds. These results indicate that, all our compounds exhibit metallic behavior and this metallicity is due to the p-d hybridization. The elastic constants have also evaluated by the Hex-elastic package. The mechanical stability reveal that, all our compounds are stable mechanically. The bulk modulus, shear modulus, Young’s modulus, Poisson’s ratio and Cauchy pressure were calculated and discussed in detail. Furthermore, the temperature and pressure effect on: Bulk modulus, Debye temperature and heat capacity at constant volume and constant pressure CV and CP, respectively have been investigated by the quasi-harmonic Debye model.

Theoretical study of phase stability, electronic and magnetic properties of Rh2CrGe1-xAlx (x = 0, 0.25, 0.50, 0.75 and 1) Heusler alloys by FP-LAPW method

First-principle calculations were performed within the framework of the density functional theory (DFT) using FP-LAPW method as implemented in WIEN2k code to determine the structural stability, electronic and magnetic properties of Rh$_2$CrGe$_{1-x}$Al$_x $($x = 0$, $0.25$, $0.50$, $0.75$ and $1$). The results showed that for Rh$_2$CrAl and Rh$_2$CrGe, the Cu$_2$MnAl-type structure is energetically more stable than Hg$_2$CuTi-type structure at the equilibrium volume. The calculated densities of states for Rh$_2$CrAl and Rh$_2$CrGe show half-metallic and nearly half-metallic behavior, respectively. Rh$_2$CrGe$_{1-x}$Al$_x$ ($x = 0.25$, $0.50$, $0.75$) these alloys show a half-metallic character, and these compounds are predicted to be good candidates for spintronic applications.

First-principles electronic structure, phonon properties, lattice thermal conductivity and prediction of figure of merit of FeVSb half-Heusler

In this work, we have studied the electronic structure of a promising thermoelectric half-Heusler FeVSb using FP-LAPW method and SCAN meta-GGA including spin–orbit coupling. Using the obtained electronic structure and transport calculations we try to address the experimental Seebeck coefficient S of FeVSb samples. The good agreement between the experimental and calculated S suggests the band gap could be ∼0.7 eV. This is supported by the obtained mBJ band gap of ∼0.7 eV. Further, we study and report the phonon dispersion, density of states and thermodynamic properties. The effect of long range Coulomb interactions on phonon frequencies are also included by nonanalytical term correction. Under quasi-harmonic approximation, the thermal expansion behaviour up to 1200 K is calculated. Using the first-principles anharmonic phonon calculations, the lattice thermal conductivity κ ph of FeVSb is obtained under single-mode relaxation time approximation considering the phonon-phonon interaction. At 300 K, the calculated κ ph is ∼18.6 W m−1 K−1 which is higher compared to experimental value. But, above 500 K the calculated κ ph is in good agreement with experiment. A prediction of figure of merit ZT and efficiency for p-type and n-type FeVSb is made by finding out optimal carrier concentration. At 1200 K, a maximum ZT of ∼0.66 and ∼0.44 is expected for p-type and n-type FeVSb, respectively. For p-type and n-type materials, maximum efficiency of ∼12.2% and ∼6.0% are estimated for hot and cold temperature of 1200 K and 300 K, respectively. A possibility of achieving n-type and p-type FeVSb by elemental doping/vacancy is also discussed. Our study is expected to help in further exploring the thermoelectric material FeVSb.

Study of magnetic, thermoelectric and optical behaviors of PbMO3 (M = V, Mn) perovskites using DFT approach

This work reports the magnetic, thermoelectric and optical behaviors of PbMO3 (M = V, Mn) perovskites analyzed using density functional theory based FP-LAPW method. The electronic structures are computed using mBJ potential. The antiferromagnetic state stability at the ground state is investigated by contrasting released energies in the ferromagnetic, antiferromagnetic and nonmagnetic states. The origin of magnetism is described by comparing the determined crystal field, Jahn-Teller and exchange energies. Thermoelectric response is investigated in terms of important parameters demonstrating that PbVO3 can exhibit higher figure of merit than PbMnO3. Various optical parameters are computed to reveal optical device applications and Penn’s model is also verified. The electronic properties elucidate reducing band gap in the semiconducting perovskites when moving from V to Mn cation, due to which, optical absorption edges are shifted to the lower energies suggesting energy harvesting device applications.

DFT-focused estimation of mechanical, thermoelectric and thermodynamic properties of ACdF3(A=K, Rb, Cs) fluroperovskites

Structural, electronic, mechanical, thermodynamic and thermoelectric properties of Alkaline fluroperovskites ACdF3(A[Formula: see text]=[Formula: see text]K, Rb, Cs) have been explored using the FP-LAPW method from the perspective of density functional theory (DFT) as employed in the Wien2k package within the generalized gradient approximation (GGA) as well as the local spin density approximation (LSDA). The volume optimization calculations of these materials agree well with experimental as well as available theoretical values. From the energy dispersion curves as well as DOS plots, all the investigated alkali fluroperovskites are found to have an indirect bandgap in [Formula: see text]-M direction using both approximations. The second-order elastic constants as well as mechanical properties such as Young’s modulus, shear modulus, density, anisotropic factor, B/G[Formula: see text] ratio are also computed for these materials. In order to study the thermal and vibrational effects on the studied fluroperovskites, we have employed the quasi-harmonic Debye model that uses a set of energy versus volume calculations. The effects of temperature as well as pressure on the structural parameters are also studied using the non-equilibrium Gibbs function. The transport properties of these perovskites have been investigated using BoltzTrap Code. Comparatively, a good figure of merit of these compounds reveals their possible use in thermoelectric applications.

Effect of Mn doping in mechanical properties of Cd1−xMnxTe2

We have investigated the structural and elastic properties of Cd1−xMnxTe2 compound using the DFT based FP-LAPW method within a framework of GGA proposed by Perdew–Burke–Ernzerhof. These compounds are found to be stable in the pyrite phase, in agreement with the available experimental reports. The results of the equilibrium lattice constants and bulk moduli are in comparison with experimental and theoretical studies of CdTe2. The analysis of elastic constant at relaxed positions reveals the ductile nature of the compound with ionic contribution in the inter atomic bonding, whereas as the concentration of Mn increases the sample material starts to show a brittle nature with covalent bonding. The substitution of Mn atoms on the Cd site affect their mechanical properties (bulk modulus, young modulus, shear modulus) of the compound which have been reported. The formation energy was also calculated which predicted that the compound is thermodynamically stable and the stability increases with concentration of the Mn.

Evaluation of structural, electronic, thermoelectric, and optical results of C‐doped HfO 2 by first‐principle's investigation

In this work, we report the ab initio numerical simulation investigation on the crystal lattice, electronic structure, optical, and transport properties of pure and C-doped crystalline hafnium dioxide (c-HfO2) using FP-LAPW method. Different exchange correlation functionals like generalized gradient approximation (GGA) of PBE-sol and Tran and Blaha's modified Becke-Johnson exchange potential (mBJ) within density functional theory have been used. Two kinds of defects in cubic pure HfO2 have been investigated: one is substitution of Hf atom by C impurity and other substitution of O atom by C impurity in crystalline HfO2. The computed results indicate that impurity energy bands as a result of 2p states of C are found to present in the band gap of c-HfO2. Few of these bands are present at the conduction band minimum, which results to a noteworthy band gap contraction, and hence electrons close to Fermi level get transferred in doped c-HfO2. We have also analysed the dielectric function, absorption coefficient, optical conductivity, optical function, electron energy loss, and reflectivity for both pure HfO2 and doped with C. Furthermore, the temperature-dependent transport properties of C-doped HfO2 are also discussed in terms of Seeback coefficient, thermal conductivities, electronic conductivities, power factor, and figure of merit in the temperature range 0 to 1200 K. The calculated value of PF for pure HfO2 was found to increase from 0.01 × 1012 WK−2m−1s−1 at 50 K to 1.79 × 1012 WK−2m−1s−1 at 1200 K and for HfO2(1 − x)Cx it was found to increase from 0.06 × 1012 WK−2m−1s−1 at 50 K to 0.25 × 1012 WK−2m−1s−1 at 1200 K.