First-principles Full-potential Linearized Augmented Plane Wave Research Articles

Mechanical and Thermodynamic Properties of Half-metallic Ferromagnetism Containing Cobalt and Titanium

We have studied the structural, electronic, elastic, magnetic and Thermodynamic properties of Co-based full-Heusler alloys Co2TiSi and Co2TiGe. have been studied by first-principles full-potential linearized augmented plane wave (FPLAPW) method with the Generalized Gradient Approximation (GGA) based on density functional theory (DFT). This shows that the magnetic properties of the compound are dependent on electron concentration of main group element and all compunds are magnetic in their equilibrium L21 structure. The electronic structure report that, our compounds have half-metallic (HM) nature. The mechanical results show that these compounds are mechanically stable. and exhibit 100% spin polarization at the Fermi level where it can be shifted within the energy-gap. In addition, the quasi-harmonic Debye model is applied to determine the thermal properties of the alloy.

Temperature dependent magnetic Compton profiles and first-principles strategies of quaternary half-Heusler alloy Co1−xCuxMnSb(0 ⩽ x ⩽ 0.8)

Temperature dependent experimental Compton profiles of quaternary alloys Co1−xCuxMnSb (x = 0.0, 0.2, 0.6 and 0.8) when decomposed into constituent profiles show that the sp-electron spin polarization is antiferromagnetically coupled to Mn-3d moments. The orbital magnetic moments derived from combination of magnetic Compton profiles (MCPs) and magnetization measurements are found to be small. Moreover, the first-principles full potential-linearized augmented plane wave (FP-LAPW) calculations have been performed to validate the experimental investigations of spin moments and half-Heusler properties. Present experimental and theoretical work show major role of Mn atoms in building-up the absolute spin moments. Our MCP data and spin-projected density of states derived from FP-LAPW computations show an increase in sp-d interaction in conduction region on increasing the Cu concentration. Further, Ruderman–Kittel–Kasuya–Yosida-type hybridization and antiferromagnetic superexchange interactions are witnessed in the reported alloys.

Ab-initio study of mechanical, half-metallic and optical properties of Mn2ZrX (X = Ge, Si) compounds

The structural, elastic, electronic, magnetic and optical properties of Mn2 based full-Heusler alloys, Mn2ZrGe and Mn2ZrSi, were investigated by the first-principles full-potential linearized augmented plane wave (FP-LAPW) method in the framework of the Density Functional Theory. The AlCu2Mn-type structure was considered for both compounds. Based on E-V calculation, the ferromagnetic (FM) state was more stable than paramagnetic (PM) state. So, in the FM state the equilibrium lattice parameter was calculated as 5.995Å and 6.079Å for Mn2ZrSi and Mn2ZrGe respectively. The integer value 2.000µB is obtained for total magnetic moments of both compounds that is perfectly consistent with Slater-Pauling rule. These alloys in the minority spin channel have metallic property while in the majority spin channel, they have band gap that confirms their semiconductor properties. Elastic properties of the alloys such as bulk modulus B, shear modulus G, Young’s modulus E and Poisson's modulus ν were obtained. Also, optical properties like dielectric function, reflectivity, energy loss function, absorption coefficient and optical conductivity were calculated.

Erratum to: The Effect of Substitution of As for Ga on the Topological Phase and Structural, Electronic and Magnetic Properties of Mn2ZrGa Heusler Alloy

The structural, electronic, and magnetic properties and existence of the topological insulator and metal phase of full-Heusler Mn2ZrGa1−xAs x (x = 0, 0.25, 0.5, 0.75, 1) alloys are studied by using the first-principles full-potential linearized augmented plane wave (FP-LAPW) method. The electronic structure results indicate that the half-metallic character for the whole series exhibits a pseudo-gap for compounds with x = 0, 0.25, and 1 and a real gap for x = 0.5 and 0.75. It was found that the total magnetic moment decreases linearly with increasing As content and follows the Slater–Pauling rule. The results also predict that the whole series from x = 0 to 1 shows ferrimagnetic ordering with antiparallel alignment between Mn and Zr moments. The results of the topological band structure show that for the equilibrium lattice parameter, the Mn2ZrGa1−xAs x alloys have normal band order. Moreover, the effect of lattice parameter change on the band order of these alloys is investigated. By increasing the lattice parameter, the inverted band order occurs for the Mn2ZrAs compound.

A systematic study of LaAlO3 with variation of Nd doping, case of band gap tuning: A first principles method

In this paper, the structural, electronic and magnetic properties of Nd-doped rare earth aluminate, La[Formula: see text]Nd[Formula: see text]AlO3 ([Formula: see text] = 0%–100%) is studied using the first-principles full potential linearized augmented plane wave (FP-LAPW) method. The effects of partial Nd substitution for La in LaAlO3 are studied using supercell calculations. The electronic structure analysis indicates La[Formula: see text]Nd[Formula: see text]AlO3 to be a probable half metal within the spin polarized generalized gradient approximation (GGA). The direct and indirect band gaps are reported and were analyzed as a function of concentration of Nd doping on LaAlO3. The calculated magnetic moments in La[Formula: see text]Nd[Formula: see text]AlO3 were found to arise mainly from the Nd-[Formula: see text] electrons which manifest the magnetic nature of the system. The significant band gap narrowing with increase in doping concentration may find important applications in optoelectronic devices.

Study of electronic and magnetic properties in 4f electron based cubic EuAlO3: a first-principles calculation

The electronic and magnetic properties of EuAlO3 are calculated by first-principles full-potential linearized augmented plane wave (FP-LAPW) method based on density functional theory (DFT). The exchange and correlation potential is treated with different approximations: mBJ and GGA + U. Coulomb repulsion (U) has been calculated using super-cell calculations for EuAlO3. The GGA + U calculations reveal an indirect band gap of 4.6 eV for EuAlO3 in the spin down channel supporting the half metallic (HM) nature of the system. An effective integral magnetic moment also supported the HM nature of EuAlO3.

Low Thermal Gradient Czochralski growth of large CdWO4 crystals and electronic properties of (010) cleaved surface

The crystal growth of large high-quality inclusion-free CdWO4 crystals, 110 mm in diameter and mass up to 20kg, has been carried out by the Low Thermal Gradient Czochralski (LTG Cz) technique. The high-purity CdWO4(010) surface has been prepared by cleavage and high structural quality of the surface has been verified by RHEED, revealing a system of Kikuchi lines. The chemical state and electronic structure of the surface have been studied using X-ray photoelectron spectroscopy (XPS) and X-ray emission spectroscopy (XES). The total and partial densities of states of the CdWO4 tungstate were calculated employing the first-principles full potential linearized augmented plane wave (FP-LAPW) method. The results indicate that the principal contributors to the valence band of CdWO4 are the Cd 4d, W 5d and O 2p states which contribute mainly at the bottom, in the central portion and at the top of the valence band, respectively, with also significant contributions of the mentioned states throughout the whole CdWO4 valence-band region. With respect to the occupation of the O 2p states, the results of the FP-LAPW calculations are confirmed by comparison on a common energy scale of the XPS valence-band spectrum and the XES band representing the energy distribution of the O 2p states in this compound. Additionally, the FP-LAPW data allow us to conclude that the CdWO4 tungstate is a non-direct semiconductor.

Elastic and Optical Properties of Filled Skutterudite EuRu_4P_(12)

The elastic properties and optical spectra of EuRu_4P_(12) have been studied by using the first principles full-potential linearized augmented plane wave (FP-LAPW) method based on density functional theory (DFT). The calculated equilibrium lattice constant is in good agreement with the experimental result. For the first time, the numerical values of the isotropic elastic parameters and related properties, such as the bulk modulus, shear modulus, Young's modulus, Poisson's ratio, Zener anisotropy factor, Kleinman parameter, Lame's coefficients, Debye temperature, and sound velocities are estimated in the framework of the Voigt-Reuss-Hill approximation. The real and imaginary parts of the dielectric constant are also calculated as a function of photon energy. The study of the energy bands near the Fermi level shows this compound to be a semimetal and a possible candidate for thermoelectric applications.

Electrons per atom ratio determination and Hume-Rothery electron concentration rule for P-based polar compounds studied by FLAPW-fourier calculations.

The extent to which reliable electrons per atom ratio, e/a, are determined and the validity of the Hume-Rothery stabilization mechanism are ensured upon increasing ionicity are studied by applying first-principles full potential linearized augmented plane wave (FLAPW)-Fourier band calculations to as many as 59 binary compounds formed by adding elements from periods 2-6 to phosphorus in group 15 of the Periodic Table. Van Arkel-Ketelaar triangle maps were constructed both by using the Allen electronegativity data and by using an energy difference between the center-of-gravity energies of FLAPW-derived s and p partial densities of states (DOSs) for the equiatomic compounds studied. The determination of e/a and the test of the interference condition, both of which play a key role in the Hume-Rothery stabilization mechanism, were reliably made for all intermetallic compounds, as long as the ionicity is less than 50%. In the A-P (A = Li, Na, K, Rb, and Cs) compounds with ionicity exceeding 50%, however, e/a determination becomes unstable, as reflected in its P concentration dependence. New Hume-Rothery electron concentration rules were theoretically found in two families of polar compounds: skutterudite compounds TMP(3), TMAs(3), and TMSb(3) (TM = Co, Ni, Rh, and Ir; cI32) with e/a = 4.34 and TM(3)P (TM = Cr, Mn, Fe, and Ni; tI32) with e/a = 2.20.

First-principles study of electronic and elastic properties of EuCd and GdCd

The structural, electronic, elastic and mechanical properties of EuCd and GdCd have been investigated by using first-principles full-potential linearized augmented plane wave (FP-LAPW) method within density functional theory (DFT). The calculations were performed within the generalized gradient approximation (GGA) and local spin density approximation (LSDA) for the exchange–correlation potentials. The ground state properties of these compounds such as the equilibrium lattice parameter (a0), bulk modulus (B) and its pressure derivative (B′) are calculated and compared with available experimental results. The calculated lattice constant obtained with GGA is very close to the experimental values. The electronic structure reveals that these materials exhibit metallic nature. The chemical bonding is interpreted by calculating the electronic charge density plots along (110) plane which show that EuCd has ionic bonding while GdCd has covalent bonding along with some ionic characteristic. We have determined three independent elastic constants (C11, C12 and C44) at ambient pressure, which have not been calculated and measured yet. Ductility/brittleness of these compounds has been analyzed using Pugh’s rule (B/GH) and Cauchy pressure (C12–C44). Mechanical properties like shear modulus, Young’s modulus, elastic anisotropy and Poisson’s ratio are obtained from the calculated elastic constants. The Debye temperature is also estimated for future investigation.

First principle study of the electronic properties of the magnetocaloric compound Gd5Si4

The electronic structure and magnetic properties of the Gd 5 Si 4 compound have been investigated by the first principles full-potential linearized augmented plane wave (FP-LAPW) method based on density functional theory (DFT) using the WIEN2k code. The Coulomb corrected local-spin density approximation (LSDA + U) in the self-interaction correction (SIC) has been used for the exchange-correlation potential. Based on the calculated results, the ground state of Gd 5 Si 4 is found to be ferromagnetic (FM). The optimized structural parameters and magnetic properties including the lattice constants and magnetic moments are in good agreement with experimental data. The magnetic moments of the Gd atoms in Gd 5 Si 4 are smaller than that of the elemental gadolinium. The magnetic moment of Gd 5 Si 4 is found to be 37.8 μB/f.u. DOS results show that the magnetic properties of the compound depend on the hybridization between Si -3p and Gd -5d states which have an effective role in the RKKY interaction. The existence of the very flat bands at -7 eV for spin up and at +3 eV for spin down that is mainly Gd -4f characters shows that the LSDA + U method provides the better description of our systems. The obvious overlap of electron densities between the Gd1 and Si atoms indicates a covalent-like bonding between them.

Thermoelectric, band structure, chemical bonding and dispersion of optical constants of new metal chalcogenides Ba4CuGa5Q12 (Q=S, Se)

The electronic structure and dispersion of optical constants of the Ba4CuGa5S12 and Ba4CuGa5Se12 compounds were calculated by the first-principles full-potential linearized augmented plane wave (FPLAPW) method. We employed the local density approximation (LDA), generalized gradient approximation (GGA) and Engel–Vosko GGA (EVGGA) to calculate the electronic structures, Fermi surface, thermoelectric, chemical bonding and dispersion of optical constants of these compounds. By investigating the influence of replacing S by Se, it has been found that the charge density around ‘Ga’ is greater in Ba4CuGa5Se12 than Ba4CuGa5S12. Fermi surface of Ba4CuGa5S12 consists of an electronic sheet only because there is no empty region while Ba4CuGa5Se12 contains both holes and electronic sheets because this compound contains both empty and shaded region. As we replace S by Se the heights of the peaks decreases as a results the reflectivity also decreases. It is noticed that the reflectivity is over 68% (60%) for Ba4CuGa5S12 (Ba4CuGa5Se12) compounds within the energy range studied. This implies that the material will serve as a good reflector. By replacing S by Se the figure of merit values increases from 0.97 to 1.0, which shows the good thermoelectric behavior of both compounds.

NFE approximation for the e/a determination for 3d-transition metal elements and their intermetallic compounds with Al and Zn

First-principles full-potential linearized augmented plane wave (FLAPW) band calculations with subsequent FLAPW-Fourier analyses have been performed for elements from K to Cu in period 4 of the periodic table to determine the effective electrons per atom ratio (e/a). For the series of 3d-transition metals (TM), the determination of the square of the Fermi diameter , from which e/a is derived, has been recognized not to be straightforward because of the presence of a huge anomaly associated with the TM-d states across the Fermi level in the energy dispersion relation for electrons outside the muffin-tin sphere. The nearly free electron (NFE) approximation is newly devised to circumvent this difficulty. The centre of gravity energy is calculated from the energy distribution of the square of the Fourier coefficients for the FLAPW state . The NFE dispersion relation is constructed for the set of and in combination with the tetrahedron method. The resulting e/a values are distributed over positive numbers in the vicinity of unity for elements from Ti to Co. Instead, the e/a values for the early elements K, Ca and Sc and the late TM elements Ni and Cu were determined to be close to one, two, three, 0.50 and unity, respectively, using our previously designed local reading method. In addition, the composition dependence of e/a values for intermetallic compounds in X-TM (X = Al and Zn) alloy systems was studied to justify an appropriate choice between the local reading and NFE methods for respective elements.

Electronic, magnetic and structural properties of the filled skutterudite EuFe4P12: LSDA and LSDA+U calculation

The electronic density of states (DOS) and magnetic moments of the filled skutterudite EuFe4P12 have been studied by the first principles full-potential linearized augmented plane wave (FP-LAPW) method within the framework of both the local spin-density approximation (LSDA) and LSDA+U approach based on the density functional theory (DFT). The optimized lattice parameter is in reasonable agreement with the experimental value. The calculation of the density of states near the Fermi level shows the compound to be suitable for effective thermoelectric application. The exchange-splitting of Eu-4f state electrons has been analysed to explain the ferromagnetic nature of this system. The magnetic moments of EuFe4P12 are found to be 5.62μB and 8.18μB by using LSDA and LSDA+U method, respectively.

First-principles FP-LAPW calculations and X-ray spectroscopy studies of the electronic structure of Zr3V3O and Zr3V3O0.6 oxides

Electronic properties of Zr3V3O oxide, a very promising hydrogen-storage material, were studied both from theoretical and experimental points of view employing the full potential linearized augmented plane wave (FP-LAPW) method as well as X-ray photoelectron spectroscopy (XPS) and X-ray emission spectroscopy (XES). Total and partial densities of states of the constituting atoms of Zr3V3O have been derived from the FP-LAPW calculations. These data indicate that, the O 2p-like states are the dominant contributors in the bottom of the valence band, whilst the top of the valence band and the bottom of the conduction band of Zr3V3O are dominated by contributions of the V2 3d-like states, with slightly smaller contributions of the V1 3d-like states as well. Significant contributions of the Zr 4d-like states throughout the whole valence-band region and near the bottom of the conduction band are also characteristic of the electronic structure of Zr3V3O. The XPS valence-band spectra and the XES Zr Lβ2,15, V Lα and O Kα bands have been derived and compared on a common energy scale for Zr3V3O and Zr3V3O0.6 oxides. This comparison of the experimental spectra was found to be in excellent agreement with the results of the FP-LAPW calculations. In addition, the XPS Zr 3d, V 2p and O 1s core-level binding energies have been measured for Zr3V3O and Zr3V3O0.6 oxides.

Electronic and magnetic properties of SmCrSb 3 and GdCrSb 3: A first principles study

The density of states (DOS) and the magnetic moments of SmCrSb 3 and GdCrSb 3 have been studied by first principles full-potential linearized augmented plane wave (FP-LAPW) method based on density functional theory (DFT). For the exchange-correlation potential, the local-spin density approximations with correlation energy (LSDA+U) method have been used. Total and partial DOS have been computed using the WIEN2k code. DOS result shows the exchange-splittings of Cr-3 d and rare-earth (R) 4 f states electrons, which are responsible for the ground state ferromagnetic (FM) behavior of the systems. The FM behavior of these systems is strongly influenced by the average number of Cr-3 d and Sm (Gd) 4 f-electrons. The effective moment of SmCrSb 3 is found to be 7.07 μ B while for GdCrSb 3 it is 8.27 μ B. The Cr atom plays a significant role on the magnetic properties due to the hybridization between Cr-3 d and Sb-5 p states.

Ground state electronic and magnetic properties of RCrSb 3 (R=La, Ce, Nd, Gd and Dy): A first principles study

The electronic density of states (DOS) and magnetic moments of rare-earth antimonides (RCrSb 3) have been studied by the first principles full-potential linearized augmented plane wave (FP-LAPW) method based on density functional theory (DFT). For the exchange–correlation potential, the LSDA+U method is used. The effective moments of LaCrSb 3, CeCrSb 3, NdCrSb 3, GdCrSb 3, and DyCrSb 3 were found to be 3.03 μ B , 3.73 μ B , 5.77 μ B , 8.27 μ B and 4.69 μ B respectively. The exchange-splittings of Cr-3d state electrons and 4f-states of rare earth elements were analyzed to explain the magnetic nature of these systems. The Cr atom plays a significant role on the magnetic properties due to the hybridization between Cr-3d and Sb-5p state orbitals. The results obtained are compared and found to be in close agreement with the available data.

Electronic and magnetic properties of NdCrSb 3: A first principles study

The electronic and magnetic properties of NdCrSb 3 are calculated by the first principles full-potential linearized augmented plane wave (FP-LAPW) method based on the density functional theory (DFT). Density of states (DOS), magnetic moments and band structures of the system are presented. For the exchange and correlation energy, local spin density approximation (LSDA+ U) with the inclusion of Hubbard potential U is used. Our calculation shows that the 3d state electron of Cr and 4f state electrons of Nd contribute to the total DOS and the band structures. The effective magnetic moment is found to be 5.77μ B, which is comparable to the earlier experimental results of NdCrSb 3.

Electronic structure of Ag5Zn8, Ag9In4 and Mn3In gamma-brasses studied by FLAPW band calculations

First-principles FLAPW (full-potential linearized augmented plane wave) band calculations were performed, using the WIEN2k program package, for three isostructural gamma-brasses, Ag5Zn8, Ag9In4 and Mn3In. The FsBz (Fermi surface–Brillouin zone) interactions were successfully extracted from the case.output1 file generated from WIEN2k. This has opened a way for any users to perform FLAPW-Fourier analyses using the commercially available WIEN2k package. From the FLAPW-Fourier spectrum, it was found that the square of the reciprocal lattice vector, = 18, for the set of {411} and {330} lattice planes is responsible for opening a pseudogap in Ag5Zn8 and Ag9In4 gamma-brasses through FsBz interactions. In the case of Mn3In, the importance of the d-states mediated FsBz interaction involving = 18 is emphasized.

Electronic structure of FeWO 4 and CoWO 4 tungstates: First-principles FP-LAPW calculations and X-ray spectroscopy studies

Total and partial densities of states of the constituent atoms of iron tungstate, FeWO 4, and cobalt tungstate, CoWO 4, have been calculated using the first-principles self-consistent full potential linearized augmented plane wave (FP-LAPW) method. The results obtained reveal that the O 2p-like states are the dominant contributors into the valence band of the tungstates under consideration, whilst the bottom of the conduction band of FeWO 4 and CoWO 4 is dominated by contributions of the empty Fe 3d- and Co 3d-like states, respectively. The FP-LAPW data indicate that the O 2p-like states contribute mainly into the top of the valence band, with also significant contributions throughout the whole valence-band region, of FeWO 4 and CoWO 4 compounds. Other significant contributors into the valence-band region are the Fe 3d- and W 5d-like states in FeWO 4 and the Co 3d- and W 5d-like states in CoWO 4. All the above d-like states contribute throughout the whole valence-band region of the tungstates under consideration, however maximum contributions of the W 5d-like states occur in the lower, whilst the Fe (Co) 3d-like states in the upper portions of the valence band, respectively. To verify the above FP-LAPW data, the X-ray emission bands representing the energy distributions of mainly the valence O p-, Fe (Co) d-, Fe (Co) p- and W d-like states were measured and compared on a common energy scale with the X-ray photoelectron valence-band spectrum of the corresponding tungstate. The experimental data were found to be in good agreement with the theoretical FP-LAPW results for the electronic structure of FeWO 4 and CoWO 4 compounds.