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The structural, electronic, magnetic and elastic properties of the ternary chalcogenides KMnQ2 (Q=O, S, Se, Te) crystals were investigated by means of spin-polarized density functional theory calculations. The 3d orbitals of the Mn atoms were treated using the GGA+U approach. The calculated equilibrium structural parameters agree well with the experimental data. Based on the analysis of the spin-polarized band structures and density of states, we predict the half-metallic character of the studied compounds, with a half-metallic gap of 1.38 eV, 0.53 eV, 0.37 eV and 0.14 eV for KMnO2, KMnS2, KMnSe2 and KMnTe2, respectively, and a total magnetic moment of 4.00μB per unit-cell for all considered structures. The examined properties for the title compounds include also the single-crystal elastic constants, bulk modulus, shear modulus, Young's modulus and Poisson's ratio.

Using the first-principles density functional calculations, the structural, electronic and magnetic properties of the Fe 2 XAl (X=Cr, Mn, Ni) compounds in both the Hg 2 CuTi and Cu 2 MnAl-type structures were studied by the full-potential linearized augmented plane waves (FP-LAPW) method. The exchange and correlation potential is treated by the generalized-gradient approximation (GGA) where the results show that the Cu 2 MnAl-type structure is energetically more stable than the Hg 2 CuTi-type structure for the Fe 2 CrAl and Fe 2 MnAl compounds at the equilibrium volume. The full Heusler compounds Fe 2 XAl (X=Cr, Mn) are half-metallic in the Cu 2 MnAl-type structure. Fe 2 NiAl has a metallic character in both CuHg 2 Ti and AlCu 2 Mn-type structures. The total magnetic moments of the Fe 2 CrAl and Fe 2 MnAl compounds are 1.0 and 2.0 μ B , respectively, which are in agreement with the Slater–Pauling rule M tot =Z tot − 24.

In this work, we have investigated the structural, phase transition, optoelectronic and magnetic properties of AmO 2 using the full potential linearized augmented plane wave plus local orbital (FP-LAPW+lo) method. The exchange-correlation potential was treated with the generalized gradient approximation (GGA). Moreover, the GGA+ U approximation (where U denotes the Hubbard Coulomb energy U term) is employed to treat the f electrons properly. The structurally stable AmO 2 compound is the Fm3m phase and at a pressure between 40 and 60 GPa underwent a phase transition to the Pnma phase. Our present calculations have considered ferromagnetic and simple antiferromagnetic ground states and the AF state is favored. However, the experimental situation suggests a complex magnetic structure, perhaps involving multipolar ordering. Our band structure calculation with GGA and GGA+ U predicted the metallic behavior of AmO 2 ; however, with the spin–orbit coupling (SOC) added to the Coulomb energy U term, semiconducting ground states with antiferromagnetism is correctly predicted. The projected density of states from the energy-band structure indicates that the band gap opening is governed by the partially filled Am “5 f ” state, and the calculated gap is approximately 1.29 eV. Moreover, the optical properties reveal strong response of AmO 2 in the UV region.

The structural, electronic and magnetic properties of half-Heusler CoFeIn and full-Heusler Co 2 FeIn alloys have been investigated by using the state of the art full-potential linearized augmented plane wave (FP-LAPW) method. The exchange-correlation potential was treated with the generalized gradient approximation (PBE-GGA) for the calculation of the structural properties, whereas the PBE-GGA+ U approximation (where U is the Hubbard Coulomb energy term) is applied for the computation of the electronic and magnetic properties in order to treat the “ d ” electrons. The structural properties have been calculated in the paramagnetic and ferromagnetic phases where we have found that both the CoFeIn and Co 2 FeIn alloys have a stable ferromagnetic phase. The obtained results of the spin-polarized band structure and the density of states show that the CoFeIn alloy is a metal and the Co 2 FeIn alloy has a complete half-metallic nature. Through the obtained values of the total spin magnetic moment, we conclude that in general, the Co 2 FeIn alloy is half-metallic ferromagnet material whereas the CoFeIn alloy has a metallic nature.

The structural, mechanical, electronic and magnetic properties of the series of Heusler alloys CoFeMnZ (Z=Si, As, and Sb) have been investigated theoretically. The objective is to seek for stable half-metallic ferromagnets materials with Curie temperatures higher than room temperature. The series of CoFeMnZ (Z=Si, As and Sb) is found to exhibit half-metallic ferromagnetism with high magnetic moment and the localized moment in these magnetic compounds resides at the Mn atom. It has been observed that all our compounds have high Curie temperatures with high spin polarizations.

The structural stabilities, electronic and magnetic properties of Co 2− x Cr x MnAl alloys with ( x =0,1 and 2) were investigated using the full-potential linear muffin-tin orbital (FP-LMTO) method, in the framework of the density functional theory (DFT) within the generalized gradient approximation (GGA) for the exchange correlation functional. The ground state properties including lattice parameter, bulk modulus for the two considered crystal structures Hg 2 CuTi-Type (X-Type) and Cu 2 MnAl-Type (L2 1 -Type) are calculated. The half-metallicity within ferromagnetic ground state starts to appear in CoCrMnAl and Cr2MnAl. In the objective for the proposition of the new HM-FM in the Full-Heusler alloys, our results classified CoCrMnAl as new HM-FM material with high spin polarization.

First-principles calculations have been used to study the structural, elastic, electronic, magnetic and thermal properties of zinc blende Zn1−xVxTe for x=0, 0.25, 0.50, 0.75 and 1 using the full-potential linearized augmented plane wave method (FP-LAPW) based on spin-polarized density functional theory (DFT). The electronic exchange-correlation potential is approached using the spin generalized gradient approximation (spin-GGA). The structural properties of the Zn1−xVxTe alloys (x=0, 0.25, 0.50, 0.75 and 1) are given for the lattice constants and the bulk moduli and their pressure derivatives. The elastic constants C11, C12 and C44 are calculated using numerical first-principles calculations implemented in the WIEN2k package. An analysis of the band structures and the densities of states reveals that Zn0.50V0.50Te and Zn0.75V0.25Te exhibit a half-metallic character, while Zn0.25V0.75Te is nearly half-metallic. The band structure calculations are used to estimate the spin-polarized splitting energies Δx(d) and Δx(pd) produced by the V(3d)-doped and s(p)–d exchange constants N0α (conduction band) and N0β (valence band). The p–d hybridization reduces the magnetic moment of V from its atomic charge value of 3µB and creates small local magnetic moments on the nonmagnetic Zn and Te sites. Finally, we present the thermal effect on the macroscopic properties of these alloys, such as the thermal expansion coefficient, heat capacity and Debye temperature, based on the quasi-harmonic Debye model.

In this work, first-principles calculations of the structural, electronic and magnetic properties of Heusler compounds Fe 2 MnAl, Fe 2 MnSi and alloy Fe 2 MnSi 0.5 Al 0.5 are presented. We have applied the full-potential linearized augmented plane waves plus local orbitals (FP-L/APW+lo) method based on the density functional theory (DFT). For the exchange and correlation potential the generalized-gradient approximation (GGA) is used. It is shown that the calculated lattice constants and spin magnetic moments are in good agreement with the available theoretical and experimental data. The calculated atomic resolved densities of states of Fe 2 MnAl, Fe 2 MnSi indicate half-metallic behavior with vanishing electronic density of states for minority spin at the Fermi level, which yields perfect spin polarization while for Fe 2 MnSi 0.5 Al 0.5 shows nearly half-metallic behavior with small spin-down electronic density of states at the Fermi level.

In this study we present investigations pertaining to structural, elastic, electronic, magnetic and optical properties of RbSrC, RbSrSi and RbSrGe half-Heusler compounds. To carry out this study, full potential (FP) linearized augmented plane wave (LAPW), a scheme of calculations developed within the framework of density functional theory (DFT), is employed. To incorporate the exchange correlation (XC) energy and corresponding potential into the total energy calculations, generalized gradient approximation (GGA) parameterized by Wu-Cohen is taken into account. Analysis of band structures and densities of states (DOS) profiles illustrate the conducting nature in spin down state and the semiconducting nature in spin-up state. The bonding nature discussed via electron charge density plot reveals strong ionic bonding character of these compounds. At ambient conditions, calculations for elastic constants (Cij) and their related elastic moduli are also performed which point to their brittle character. The compounds are found to be ferromagnetic with 1 μB. The magnetic moment decreases from its integer value at high pressures for these compounds.

Effect of spin polarization on the electronic and thermoelectric properties of double pervoskites La 2 NiMnO 6 and La 2 CoMnO 6 are studied using the full-potential linearized augmented plane wave method. Further magnetic properties of the compound are also determined. Both compounds are indirect bandgap ferromagnetic materials. La 2 NiMnO 6 compound has a large band gap energy as compared to La 2 CoMnO 6 compound in both spin up and spin down states. The electrical conductivity, thermal conductivity and thermoelectric power increase with temperature for both the compounds in the spin up state, while the spin down state unchanged with the increase of temperature. There is no significant variation observed in Seebeck coefficient S with temperature for spin up state while the Seebeck coefficient decrease with the increase of temperature in both compounds for spin down state. The calculated total magnetic moments for both compounds reveals the strong ferromagnetic nature.

Based on first principles spin-polarized density functional theory, the structural, elastic electronic and magnetic properties of Zn 1− x V x Se (for x =0.25, 0.50, 0.75) in zinc blende structure have been studied. The investigation was done using the full-potential augmented plane wave method as implemented in WIEN2k code. The exchange-correlation potential was treated with the generalized gradient approximation PBE-GGA for the structural and elastic properties. Moreover, the PBE-GGA+ U approximation (where U is the Hubbard correlation terms) is employed to treat the “ d ” electrons properly. A comparative study between the band structures, electronic structures, total and partial densities of states and local moments calculated within both GGA and GGA+ U schemes is presented. The analysis of spin-polarized band structure and density of states shows the half-metallic ferromagnetic character and are also used to determine s ( p ) -d exchange constants N 0 α (conduction band ) and N 0 β (valence band) due to Se(4 p )–V(3 d ) hybridization. It has been clearly evidence that the magnetic moment of V is reduced from its free space change value of 3 µ B and the minor atomic magnetic moment on Zn and Se are generated.