Effect of Co substitution on Ni2_{2}MnGe Heusler alloy: ab initio study

Ab initio calculations shown that the Co substitution instead of Ni in Ni$_{2}$MnGe with the L2$_{1}$ crystallographic structure leads to a decrease of the lattice constant and an increase of the total magnetic moment of the Ni$_{2-x}$Co$_{x}$MnGe compounds. The Mn(B) has the largest local moment above $3~\mu_{B}$ coupled parallel to moments on the Ni(A,C) and Co(A,C), which are found in the ranges of $0.19\div0.26~\mu_{B}$ for Ni(A,C) and $1.03\div0.97~\mu_{B}$ for Co(A,C) for studied range of $x$. Using the results stemming from the total energy calculations, the values of bulk modulus and its pressure derivatives are estimated according to the Murnaghan EOS.Comment: 3 pages, 3 figures; The European Conference Physics of Magnetism 2017; submitted to Acta Physica Polonica

Orthorhombic phase of La0.5_{0.5}Bi0.5_{0.5}NiO3_{3} studied by first principles

The aim of presented first principles study of La$_{0.5}$Bi$_{0.5}$NiO$_{3}$ is to investigate electronic structure of orthorhombic phase Pbnm. The calculations show that metallicity and magnetism of the system are strongly related with hybridization between Ni 3d and O 2p. To improve the quality of the electronic structure description of the system, especially the treatment of correlation for the Ni 3d, we employ GGA, LDA, and GGA+U, LDA+U. The LSDA results give good agreement with experiment. Thus, the screening effects originating from the hybridized 3d and O 2p electrons are sufficiently strong that they reduce the electronic correlations in the La$_{0.5}$Bi$_{0.5}$NiO$_{3}$, making it a weakly correlated metal.Comment: 4 pages, 3 figures; The European Conference Physics of Magnetism 2017, submitted to Acta Physica Polonica

Electronic structure and X-ray photoelectron spectra of YNi4B compound

The electronic structure of the tern ary Y Ni4 B compoun d, crystalli zin g in the hexagonal CeCo4 B structure ( P 6= m m m space group ), was studied by X -ray photo electron spectroscopy and ab initio calculations. Core levels and the valence band were investigated. T he X- ray photo electron spectroscopy valence band is compared with that obtained from ab initi o calculations. The valence band spectrum at the Fermi level exhibits the domination of the Ni( 3 d ) states, which are hybridized with 4d states of Y and 2p states of B. The theoretical electronic specific heat coeffcient Û derived from N ( E F ) is about 11.33 mJ /(mol K 2 ) for exp erimental lattice parameters. T he calculated bulk modulus is B 0 = 1 :61632 Mbar

First-principles study of lattice instabilities in the ferromagnetic martensite Ni2_2MnGa

The phonon dispersion relations and elastic constants for ferromagnetic Ni$_2$MnGa in the cubic and tetragonally distorted Heusler structures are computed using density-functional and density-functional perturbation theory within the spin-polarized generalized-gradient approximation. For $0.9<c/a<1.06$, the TA$_2$ tranverse acoustic branch along $[110]$ and symmetry-related directions displays a dynamical instability at a wavevector that depends on $c/a$. Through examination of the Fermi-surface nesting and electron-phonon coupling, this is identified as a Kohn anomaly. In the parent cubic phase the computed tetragonal shear elastic constant, C$^\prime$=(C$_{11}-$C$_{12}$)/2, is close to zero, indicating a marginal elastic instability towards a uniform tetragonal distortion. We conclude that the cubic Heusler structure is unstable against a family of energy-lowering distortions produced by the coupling between a uniform tetragonal distortion and the corresponding $[110]$ modulation. The computed relation between the $c/a$ ratio and the modulation wavevector is in excellent agreement with structural data on the premartensitic ($c/a$ = 1) and martensitic ($c/a$ = 0.94) phases of Ni$_2$MnGa.Comment: submitted to Phys. Rev.

Electronic Structure and Martensitic Transformation in Ni2\text{}_{2} MnGa Heusler Alloy

The electronic structure of the Ni$\text{}_{2}$MnGa Heusler alloy has been investigated for martensitic transformation β$\text{}_{1}$ → β'$\text{}_{1}$ → β"$\text{}_{1}$ → β'''$\text{}_{1}$ by the self-consistent TB-LMTO method. The distortion influences the shape of the densities of states. The β$\text{}_{1}$ is the most stable phase. We present the values of total and local magnetic moments for all phases of Ni$\text{}_{2}$MnGa alloy

Effect of Co substitution on Ni₂MnGe Heusler alloy: ab initio study

Ab initio calculations shown that the Co substitution instead of Ni in Ni₂MnGe with the L2₁ crystallographic structure leads to a decrease of the lattice constant and an increase of the total magnetic moment of the Ni_{2-x}Co_{x}MnGe compounds. The Mn(B) has the largest local moment above 3 μ_{B} coupled parallel to moments on the Ni(A,C) and Co(A,C), which are found in the ranges of 0.19÷0.26 μ_{B} for Ni(A,C) and 1.03÷0.97 μ_{B} for Co(A,C) for studied range of x. Using the results stemming from the total energy calculations, the values of bulk modulus and its pressure derivatives are estimated according to the Murnaghan EOS

Effect of Small Pt Doping on the Electronic Structure of NiMnSb Half-Heusler Alloys

The effect of small Pt doping on the electronic and magnetic properties of NiMnSb compound were studied using the spin-polarised tight-binding linear muffin-tin orbital method. The electronic structure of half-Heusler alloys depends on the relative arrangement of the atoms in the unit cell, changing from half-metal to metal. The local ordering drastically influences the value of the band gap. The self-consistent band calculations were performed for the experimental lattice constant and for the lattice parameter estimated from the minimum of the total energy

Modeling Thermal Expansion of Ni2MnGeNi_{2}MnGe

The present study of $Ni_{2}MnGe$ is focused on describing the thermal properties of the alloy in the framework of first-principles electronic structure calculations coupled with a Debye treatment of the vibrating lattice. The electronic structure of $Ni_{2}MnGe$ has been studied using the full-potential nonorthogonal local-orbital minimum basis method. Two approximations for Grüneisen parameter γ, i.e. Slater's and Dugdale and MacDonald's expressions were assumed

Comparative Study of Compressibility of Ni2MnXNi_2MnX (X=In, Sn, Sb) Heusler Alloys

The present study is focused on the compressibility of $Ni_2MnX$ (X = In, Sn, Sb) Heusler alloys, which were investigated from the first principles. The study of the pressure effect on the magnetic properties of $Ni_2MnX$ (X = In, Sn, Sb) predicted the decrease in the total magnetic moment from ambient pressure to pressure above 20 GPa

Strained Tetragonal Bain Paths in Fe3\text{}_{3}Pt Invar

Employing the LMTO-ASA method we calculated the total energy variation of Fe$\text{}_{3}$Pt along the tetragonal distortion path connecting fcc and bcc structures for isotropic biaxial path and uniaxially strained path and compare the results with energies for the unstrained path