Electronic structure and magnetic properties of PbMO3 (M = Fe, Co, Ni) magnetic perovskites: An ab initio study

2014 ◽  
Vol 28 (29) ◽  
pp. 1450205 ◽  
Author(s):  
Aytaç Erkişi ◽  
Erdem Kamil Yıldırım ◽  
Gökhan Gökoğlu
Keyword(s):  
Transition Metal ◽  
Coulomb Interaction ◽  
Transition Metal Oxides ◽  
Density Functional ◽  
Magnetic Transition ◽  
Magnetic Moments ◽  
Local Spin Density Approximation ◽  
Electronic Band ◽  
Half Metallic ◽  
Hubbard U

We present the electronic, magnetic and structural properties of the magnetic transition metal oxides PbMO 3 (M = Fe , Co , Ni ) in cubic perovskite structure. The calculations are based on the density functional theory (DFT) within plane-wave pseudopotential method and local spin density approximation (LSDA) of the exchange-correlation functional. On-site Coulomb interaction is also included in calculations (LSDA+ U ). The systems are considered in ferromagnetic (FM) and G-type antiferromagnetic (G-AFM) order. FM structures are energetically more favored than G-AFM and than non-magnetic states for all the systems studied. The spin-polarized electronic band structures show that all the structures have metallic property in FM order without Hubbard-U interaction (U eff = 0). However, the inclusion of on-site Coulomb interaction (U eff = 7 eV ) opens a semiconducting gap for majority spin channel of PbFeO 3 and of PbNiO 3 resulting in a half-metallic character. PbCoO 3 system remains as metallic with LSDA+ U scheme. Bonding features of all structures are largely determined by the hybridizations between O–p and d-states of transition metal atoms. The partial magnetic moment of Fe atom in PbFeO 3 is enhanced by inclusion of Hubbard-U interaction (2.55 μB ⇒ 3.78 μB). Total magnetic moments of half-metallic PbFeO 3 and of PbNiO 3 compounds are very close to integer values.

scholarly journals Determination of Formation Energies and Phase Diagrams of Transition Metal Oxides with DFT+U

Materials ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 4303
Author(s):  
Daniel Mutter ◽  
Daniel F. Urban ◽  
Christian Elsässer
Keyword(s):  
Transition Metal ◽  
Metal Oxides ◽  
Phase Diagrams ◽  
Transition Metal Oxides ◽  
Density Functional ◽  
Synthesis Process ◽  
Local Exchange ◽  
Electronic Band ◽  
Formation Energies

Knowledge about the formation energies of compounds is essential to derive phase diagrams of multicomponent phases with respect to elemental reservoirs. The determination of formation energies using common (semi-)local exchange-correlation approximations of the density functional theory (DFT) exhibits well-known systematic errors if applied to oxide compounds containing transition metal elements. In this work, we generalize, reevaluate, and discuss a set of approaches proposed and widely applied in the literature to correct for errors arising from the over-binding of the O2 molecule and from correlation effects of electrons in localized transition-metal orbitals. The DFT+U method is exemplarily applied to iron oxide compounds, and a procedure is presented to obtain the U values, which lead to formation energies and electronic band gaps comparable to the experimental values. Using such corrected formation energies, we derive the phase diagrams for LaFeO3, Li5FeO4, and NaFeO2, which are promising materials for energy conversion and storage devices. A scheme is presented to transform the variables of the phase diagrams from the chemical potentials of elemental phases to those of precursor compounds of a solid-state reaction, which represents the experimental synthesis process more appropriately. The discussed workflow of the methods can directly be applied to other transition metal oxides.

Half-metallic properties of the new Ti2YPb(Y = Co, Fe) Heusler alloys

2015 ◽  
Vol 29 (27) ◽  
pp. 1550175 ◽  
Author(s):  
Moaid K. Hussain ◽  
G. Y. Gao ◽  
Kai-Lun Yao
Keyword(s):  
Density Functional ◽  
Magnetic Moments ◽  
Heusler Alloys ◽  
Lattice Parameter ◽  
Generalized Gradient ◽  
Electronic Band ◽  
Experimental Realization ◽  
Half Metallic ◽  
Practical Applications ◽  
Parameter Values

The half-metallic properties of Ti2YPb(Y = Co, Fe) Heusler alloys with a CuHg2Ti-type structure were examined within the frame of the density functional theory and the Perdew–Burke–Ernzerh of generalized gradient approximation (GGA). Analysis of the electronic band structures and density of states for Ti2YPb(Y = Co, Fe) revealed that the spin-up bands are metallic, whereas the spin-down bands exhibit gaps of 0.73 and 0.70 eV, respectively. The magnetic moments calculated for the Ti2YPb(Y = Co, Fe) alloys were found to be equal to 3 [Formula: see text]/f.u. and 2 [Formula: see text]/f.u., values which both follows the Slater–Pauling rule of [Formula: see text]. The compounds’ negative enthalpy values should encourage their experimental realization in the future. The bandgap was elucidated to be mainly determined by the bonding and antibonding states created from the hybridizations of the d states between the Ti(1)–Ti(2) coupling and the Y = Co, Fe atom. The half-metallic properties of the Ti2YPb(Y = Co, Fe) compounds were found to be insensitive to lattice distortion, with full spin polarization achievable within a large range of lattice parameter values, making the alloys suitable for use in practical applications.

scholarly journals Determination of Formation Energies and Phase Diagrams of Transition Metal Oxides with DFT+U

2020 ◽  
Author(s):  
Daniel Mutter ◽  
Daniel F. Urban ◽  
Christian Elsässer
Keyword(s):  
Transition Metal ◽  
Metal Oxides ◽  
Phase Diagrams ◽  
Transition Metal Oxides ◽  
Density Functional ◽  
Synthesis Process ◽  
Local Exchange ◽  
Electronic Band ◽  
Formation Energies

Knowledge about the formation energies of compounds is essential to derive phase diagrams of multi-component phases with respect to elemental reservoirs. The determination of formation energies using common (semi-)local exchange-correlation approximations of density functional theory (DFT) exhibits well-known systematic errors if applied to oxide compounds containing transition metal elements. In this work, we generalize, reevaluate and discuss a set of approaches proposed and widely applied in the literature to correct for errors arising from the over-binding of the O2 molecule and from correlation effects of electrons in localized transition-metal orbitals. The DFT+U method is exemplarily applied to iron oxide compounds, and a procedure is presented to obtain U values, which lead to formation energies and electronic band gaps comparable to experimental values. Using such corrected formation energies, we derive the phase diagrams for LaFeO3, Li5FeO4 and NaFeO2, which are promising materials for energy conversion and storage devices. A scheme is presented to transform the variables of the phase diagrams from the chemical potentials of elemental phases to those of precursor compounds of a solid-state reaction, which represents the experimental synthesis process more appropriately. The discussed workflow of methods can directly be applied to other transition metal oxides.

Magnetic Volume Effect of Hydrogen Diffusion in Palladium

2020 ◽  
Vol 310 ◽  
pp. 29-33
Author(s):  
Sarantuya Nasantogtokh ◽  
Xin Cui ◽  
Zhi Ping Wang
Keyword(s):  
Transition Metal ◽  
Density Of States ◽  
Density Functional ◽  
Hydrogen Diffusion ◽  
Magnetic Moments ◽  
Interstitial Site ◽  
Volume Effect ◽  
Face Centered Cubic ◽  
Hydrogen Atoms ◽  
Octahedral Interstitial Site

The electronic and magnetic properties of palladium hydrogen are investigated using first-principles spin-polarized density functional theory. By studying the magnetic moments and electronic structures of hydrogen atoms diffusing in face-centered cubic structure of transition metal Pd, we found that the results of magnetic moments are exactly the same in the two direct octahedral interstitial site-octahedral interstitial site diffusion paths-i.e. the magnetic moments are the largest in the octahedral interstitial site, and the magnetic moments are the lowest in saddle point positions. We also studied on the density of states of some special points, with the result that the density of states near the Fermi level is mainly contributed by 4d electrons of Pd and the change of magnetic moments with the cell volume in the unit cell of transition metal Pd with a hydrogen atom.

Ferrimagnetic Half-Metallicity of the New Quaternary Heusler Alloy CoCrScIn: FP-LAPW Method

SPIN ◽  
2021 ◽  
Vol 11 (02) ◽  
pp. 2150017
Author(s):  
Halima Hamada ◽  
Keltouma Boudia ◽  
Friha Khelfaoui ◽  
Kadda Amara ◽  
Toufik Nouri ◽  
...  
Keyword(s):  
Magnetic Moment ◽  
Density Functional ◽  
Structural Parameters ◽  
Magnetic Transition ◽  
Plane Waves ◽  
Full Potential ◽  
Half Metallicity ◽  
Metallic Behavior ◽  
Magnetic Transition Temperature ◽  
Half Metallic

The structural, electronic, elastic and magnetic properties of CoCrScIn were investigated using first principle calculations with applying the full-potential linearized augmented plane waves (FP-LAPW) method, based totally on the density functional theory (DFT). After evaluating the results, the calculated structural parameters reveal that CoCrScIn compound is stable in its ferrimagnetic configuration of the type-III structure. The mechanical properties show its brittle and stiffer behavior. The formation energy value showed that CoCrScIn can be experimentally synthesized. Additionally, the obtained band structures and density of states (DOS) reflect the half-metallic behavior of CoCrScIn, with an indirect bandgap of 0.43[Formula: see text]eV. The total magnetic moment of 3[Formula: see text][Formula: see text] and half-metallic ferrimagnetic state are maintained in the range 5.73–6,79 Å. The magnetic moment especially issues from the Cr-[Formula: see text] and Co-[Formula: see text] spin-polarizations. Furthermore, the calculations of Curie temperature reveal that CoCrScIn has high magnetic transition temperature of 836.7[Formula: see text]K.

scholarly journals Free-radical gases on two-dimensional transition-metal disulfides (XS2, X = Mo/W): robust half-metallicity for efficient nitrogen oxide sensors

2018 ◽  
Vol 9 ◽  
pp. 1641-1646 ◽  
Author(s):  
Chunmei Zhang ◽  
Yalong Jiao ◽  
Fengxian Ma ◽  
Sri Kasi Matta ◽  
Steven Bottle ◽  
...  
Keyword(s):  
Free Radical ◽  
Transition Metal ◽  
Density Functional ◽  
Single Layer ◽  
Metal Sulfides ◽  
Half Metallicity ◽  
Functional Theory ◽  
Half Metallic ◽  
Gas Molecules ◽  
High Level

The detection of single gas molecules is a highly challenging work because it requires sensors with an ultra-high level of sensitivity. By using density functional theory, here we demonstrate that the adsorption of a paramagnetic unpaired free radical gas (NO) on a monolayer of XS2 (X = Mo, W) can trigger the transition from semiconductor to half metal. More precisely, the single-layer XS2 (X = Mo, W) with NO adsorbed on it would behave like a metal in one spin channel while acting as a semiconductor in the other spin orientation. The half-metallicity is robust and independent of the NO concentration. In contrast, no half-metallic feature can be observed after the adsorption of other free radical gases such as NO2. The unique change in electronic properties after the adsorption of NO on transition-metal sulfides highlights an effective strategy to distinguish NO from other gas species by experimentally measuring spin-resolved transmission. Our results also suggest XS2 (X = Mo, W) nanosheets can act as promising nanoscale NO sensors.

scholarly journals Electronic structure, Mechanical and Thermodynamic properties of CoYSb (Y= Cr, Mo, W) half-Heusler compounds as potential spintronic materials

2021 ◽  
Author(s):  
O. T. Uto ◽  
J. O. Akinlami ◽  
S. Kenmoe ◽  
G. A. Adebayo
Keyword(s):  
Density Functional ◽  
Electronic Band Structure ◽  
Structural Phase ◽  
Covalent Bond ◽  
Stable Phase ◽  
Type I ◽  
Generalized Gradient ◽  
Electronic Density ◽  
Electronic Band ◽  
Half Metallic

Abstract The CoYSb (Y = Cr, Mo and W) compounds which are XYZ type half-Heusler alloys and also exist in the face centred cubic MgAgAs-type struc-ture conform to F ̄43m space group. In the present work, these compoundsare investigated in different atomic arrangements called, Type-I, Type-II andType-III phases, using Generalized Gradient Approximation (GGA) in the Density Functional Theory (DFT) implemented in QE (Quantum EspressoAb-Initio Simulation Package). The ferromagnetic state of these alloys is studied after investigating their stable structural phase. The calculated electronic band structure and the total electronic density of states indicated nearly half-metallic behaviour in CoMoSb with a possibility of being used in spintronic application, metallic in CoWSb and half-metallic in CoCrSb, with the minority spin band gap of 0.81 eV. Furthermore, the calculated mechanical properties predicted an anisotropic behaviour of these alloys in the stable phase. Finally, due to its high Debye temperature value, CoCrSb possesses a stronger covalent bond than CoMoSb and CoWSb, respectively.

DFT study of elastic, half-metallic and optical properties of Co2V(Al, Ge, Ga and Si) compounds

2017 ◽  
Vol 31 (14) ◽  
pp. 1750109 ◽  
Author(s):  
Heidar Khosravi ◽  
Arash Boochani ◽  
Golnaz Rasolian ◽  
Shahram Solaymani ◽  
Sirvan Naderi
Keyword(s):  
Optical Properties ◽  
Density Functional ◽  
Magnetic Moments ◽  
Elastic Stability ◽  
Metallic Behavior ◽  
Functional Theory ◽  
Spin Mode ◽  
Half Metallic ◽  
Lattice Constants ◽  
Optical Treatment

First-principles study of elastic, electronic and optical properties of full-Heusler Co2V(Al, Ge, Ga and Si) compounds are calculated through density functional theory (DFT) to obtain and compare the mentioned properties. Equilibrium lattice constants of these compounds are in good agreement with other works. Electronic calculations are shown full spin polarization at Fermi level for all compounds, so in the down spin, indirect bandgap is calculated as 0.33, 0.6, 0.2 and 0.8 eV for Co2V(Al, Ge, Ga and Si), respectively. The integer amounts of the magnetic moments are compatible with Slater–Pauling role. The optical treatment of Co2VGa is different from three other compounds. All mentioned compounds have metallic behavior by 22 eV plasmonic frequency. The imaginary part of the dielectric function for the up spin indicates that the main optical transitions occurred in this spin mode. Moreover, the elastic results show that the Co2VGa does not have elastic stability, but the other three compounds have fully elastic stability and the Co2V(Al, Ge and Si) belong to the hardness of materials.

Half-metallic properties in Co2XSn (X = Ti, V and Cr) full-Heusler compound

2019 ◽  
Vol 34 (02) ◽  
pp. 2050028 ◽  
Author(s):  
H. Abbassa ◽  
A. Labdelli ◽  
S. Meskine ◽  
Y. Benaissa Cherif ◽  
A. Boukortt
Keyword(s):  
Magnetic Moment ◽  
Density Functional ◽  
Heusler Alloys ◽  
Electronic Band ◽  
Half Metallic ◽  
Lattice Constants ◽  
Half Metal ◽  
Wide Range ◽  
Metallic Ferromagnetism ◽  
Half Metallic Ferromagnetism

First-principles calculations based on density functional theory (DFT) confirm the half-metallic ferromagnetism in both [Formula: see text] and [Formula: see text], and the nearly half-metallic ferromagnetism in [Formula: see text] Heusler alloys with the [Formula: see text]-type structure [Formula: see text]. The electronic band structures and density of states (DOS) calculations of the [Formula: see text] and [Formula: see text] compounds show that the spin-up electrons are metallic, whereas the spin-down bands are semiconducting with a gap of 0.47 eV and 0.53 eV, respectively, with 0.21 eV and 0.36 eV as a spin-flip gap, respectively. The [Formula: see text] and [Formula: see text] Heusler were half-metal compounds with magnetic moment of [Formula: see text] and [Formula: see text] at the equilibrium lattice constants [Formula: see text] Å and [Formula: see text] Å, respectively, which agrees with the Slater–Pauling rule, and have 100% polarization for a wide range of lattice parameters. The [Formula: see text] is a nearly half-metal (NHF) compound with magnetic moment of [Formula: see text] and 92.9% polarization at the equilibrium lattice constants [Formula: see text] Å and acquire half-metal behavior under the pressure 16.70 GPa.

First-Principles Study of the New Half-Metallic Ferromagnetic Quaternary-Heusler Alloys NaXNO (X=Ca, Sr, Ba)

SPIN ◽  
2020 ◽  
Vol 10 (03) ◽  
pp. 2050022 ◽  
Author(s):  
K. Belkacem ◽  
Y. Zaoui ◽  
S. Amari ◽  
L. Beldi ◽  
B. Bouhafs
Keyword(s):  
Magnetic Properties ◽  
Density Of States ◽  
First Principles ◽  
Density Functional ◽  
Heusler Alloys ◽  
Exchange Potential ◽  
Energy Calculation ◽  
Full Potential ◽  
Electronic Band ◽  
Half Metallic

The first-principles approach based on density functional theory (DFT) and the full-potential linearized augmented plane-wave method were employed to investigate the structural, elastic, electronic and magnetic properties of Na[Formula: see text]NO ([Formula: see text], Sr and Ba) quaternary half-Heusler alloys. The generalized gradient approximation (GGA) as parameterized by Perdew, Burke and Ernzerhof (PBE) and the modified Becke–Johnson exchange potential were used. As far as we know, we present our results which for the first time quantitatively account for the electronic structures and magnetic properties of Na[Formula: see text]NO ([Formula: see text], Sr and Ba) quaternary half-Heusler alloys. From the total energy calculation using three possible atomic configurations ([Formula: see text], [Formula: see text] and [Formula: see text]), it is found that the Na[Formula: see text]NO ([Formula: see text], Sr and Ba) quaternary half-Heusler alloys are more stable in the ferromagnetic [Formula: see text]-phase. From our estimated elastic constants [Formula: see text], it is found that all the considered Heusler alloys are mechanically stable in the [Formula: see text]-phase. We have also investigated the robustness of the half-metallicity with respect to the variation of lattice constants in these alloys. We have found that these alloys are half-metallic ferromagnets (HMFs) with a magnetic moment of 2[Formula: see text][Formula: see text] per formula unit at their equilibrium volumes. The spin-polarized electronic band structure and density of states of these quaternary half-Heusler alloys calculated by GGA (mBJ-GGA) show that the minority spin channels have metallic nature and the majority spin channels have a semiconductor character with half-metallic gaps of 0.49[Formula: see text]eV (2.17[Formula: see text]eV), 0.72[Formula: see text]eV (2.28[Formula: see text]eV) and 0.96[Formula: see text]eV (2.22[Formula: see text]eV) for NaCaNO, NaSrNO and NaBaNO quaternary half-Heusler alloys, respectively. Analysis of the density of states and the spin charge density of these quaternary alloys indicates that their magnetic moments mainly originate from the strong spin-polarization of 2[Formula: see text] states of N atoms and O atoms.

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