AB INITIO STUDY OF MAGNETISM IN PALLADIUM CLUSTERS SUPPORTED ON (110) SURFACE OF TiO2 RUTILE

2005 ◽  
Vol 19 (15n17) ◽  
pp. 2544-2549 ◽  
Author(s):  
P. MURUGAN ◽  
VIJAY KUMAR ◽  
YOSHIYUKI KAWAZOE
Keyword(s):  
Ab Initio ◽  
Magnetic Moments ◽  
High Mobility ◽  
Oxide Surface ◽  
Generalized Gradient ◽  
Palladium Clusters ◽  
Atomic Structures ◽  
Pseudopotential Calculations ◽  
Adsorption Energies ◽  
Tio2 Rutile

The structural, electronic, and magnetic properties of Pd n (n = 6, 13) clusters supported on (110) surface of TiO 2 rutile have been studied using ab initio ultrasoft pseudopotential calculations within generalized gradient approximation. The magnetic moments and atomic structures of these clusters have only small changes when soft landed on the oxide surface. The magnetic moments of Pd 13 cluster on TiO 2 (110) surface is reduced to 6 μB as compared to 8 μB for free cluster. Our calculations also show that the adsorption energy differences between various orientations of Pd 13 cluster on the surface of the slab are small. Therefore, nearly spherical clusters such as Pd 13 can roll and have high mobility. The calculated adsorption energies of Pd 6 and Pd 13 on the (110) surface of TiO 2 slab are approximately 2.2 and 2.4 eV, respectively.

scholarly journals Impact of Nano-Scale Distribution of Atoms on Electronic and Magnetic Properties of Phases in Fe-Al Nanocomposites: An Ab Initio Study

Nanomaterials ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 1059 ◽  
Author(s):  
Ivana Miháliková ◽  
Martin Friák ◽  
Yvonna Jirásková ◽  
David Holec ◽  
Nikola Koutná ◽  
...  
Keyword(s):  
Ab Initio ◽  
Density Functional ◽  
Nearest Neighbor ◽  
Magnetic Moments ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Α Phase ◽  
Ordered Intermetallic ◽  
Random Structures ◽  
The Impact

Quantum-mechanical calculations are applied to examine magnetic and electronic properties of phases appearing in binary Fe-Al-based nanocomposites. The calculations are carried out using the Vienna Ab-initio Simulation Package which implements density functional theory and generalized gradient approximation. The focus is on a disordered solid solution with 18.75 at. % Al in body-centered-cubic ferromagnetic iron, so-called α -phase, and an ordered intermetallic compound Fe 3 Al with the D0 3 structure. In order to reveal the impact of the actual atomic distribution in the disordered Fe-Al α -phase three different special quasi-random structures with or without the 1st and/or 2nd nearest-neighbor Al-Al pairs are used. According to our calculations, energy decreases when eliminating the 1st and 2nd nearest neighbor Al-Al pairs. On the other hand, the local magnetic moments of the Fe atoms decrease with Al concentration in the 1st coordination sphere and increase if the concentration of Al atoms increases in the 2nd one. Furthermore, when simulating Fe-Al/Fe 3 Al nanocomposites (superlattices), changes of local magnetic moments of the Fe atoms up to 0.5 μ B are predicted. These changes very sensitively depend on both the distribution of atoms and the crystallographic orientation of the interfaces.

Surface Diffusion and Incorporation Process of Adatom in Fe-Al Multilayer System

2006 ◽  
Vol 317-318 ◽  
pp. 411-414 ◽  
Author(s):  
Chi Ho Kim ◽  
In Yong Kang ◽  
Yong Chae Chung
Keyword(s):  
Total Energy ◽  
Ab Initio ◽  
Surface Diffusion ◽  
Energy Barrier ◽  
Energy Gain ◽  
Multilayer System ◽  
Large Energy ◽  
Hollow Site ◽  
Pseudopotential Calculations ◽  
Adsorption Energies

Using the ab initio pseudopotential calculations, the surface diffusion and incorporation process at the interface of Fe-Al multilayer system were quantitatively investigated. The hollow site was most stable adsorption site on both Al (001) and Fe (001) surface. The adsorption energies were 8.62 eV for Fe/Al (001) and 5.30 eV for Al/Fe (001) system. The calculated energy barriers for the surface diffusion of adatom were 0.89 eV and 0.61 eV for each system. The energy barrier for the incorporation of Fe adatom into the Al substrate was calculated to be 0.38 eV and the energy gain of the system was 0.49 eV. However, the Al adatom required relatively large energy barrier, 0.99 eV for the incorporation into the Fe substrate resulting in 0.13 eV increase in total energy of the system.

STRUCTURE STABILITY AND ELECTRONIC PROPERTIES OF CumConCO (m+n=2–7) CLUSTERS

2016 ◽  
Vol 24 (04) ◽  
pp. 1750049 ◽  
Author(s):  
JUN ZHU ◽  
XIU-RONG ZHANG ◽  
PEI-YING HUO ◽  
ZHI-CHENG YU
Keyword(s):  
Electronic Properties ◽  
Ground State ◽  
Density Functional ◽  
Adsorption Process ◽  
Magnetic Moments ◽  
Structure Stability ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Adsorption Energies ◽  
Ground State Structures

The structure stability and electronic properties of CumConCO ([Formula: see text]–7) clusters have been systematically investigated using density functional theory (DFT) within the generalized gradient approximation (GGA). The results indicate that the ground state structures of CumConCO clusters obtained by adsorbing CO molecules on the top sites of stable CumConclusters with C atoms and CO molecules have been activated during adsorption process. Cu2CO, CuCoCO, Cu3CoCO, Co4CO, Cu4CoCO and Cu3Co3CO clusters are stronger than other ground state clusters in thermodynamic stability. Cu2CO, Cu4CO and Cu6CO clusters show stronger chemical stability; Co2CO, Co4CO, Cu5CoCO, Cu3Co3CO, Cu2Co5CO and Co7CO clusters show better propensity to adsorb CO for these clusters have larger adsorption energies; Electronic states of Cu2Co3CO, CuCo4CO, Co5CO, Cu4Co3CO, Cu3Co4CO, CuCo6CO and Co7CO clusters are mainly influenced by those of 3d orbitals in Co and Cu atoms, the contribution to total magnetic moments of these clusters comes mainly from Co atoms and these clusters have high magnetism.

AB INITIO STUDY OF THE ELECTRONIC AND MAGNETIC PROPERTIES OF GRAPHENE WITH AND WITHOUT ADSORPTION OF M ATOM (M = C, N, O, F, Cl)

2018 ◽  
Vol 25 (03) ◽  
pp. 1850069 ◽  
Author(s):  
ALI I. ISMAIL ◽  
A. A. MUBARAK
Keyword(s):  
Magnetic Properties ◽  
Ab Initio ◽  
Graphene Sheet ◽  
Local Density ◽  
Magnetic Moments ◽  
Graphene Sheets ◽  
Full Potential ◽  
Ab Initio Study ◽  
Generalized Gradient ◽  
Adsorbed Atoms

We present here an ab initio study for the energetic, electronic, magnetic and optical structures of the graphene sheet with and without the adsorption of M atom (M [Formula: see text] C, N, O, F, Cl). The calculations are preformed using the full-potential linearized augmented plane wave (FP-LAPW) within the generalized gradient approximation (GGA) to describe the exchange-correlation potential. The calculations show that N prefers the bridge site, while C, O, F and Cl prefer the top site above the graphene sheet. The calculated M-graphene bond length is found to be inversely proportional to the adsorption energy. The hybridization between sp-states of the graphene sheet and M adatom is determined by the analysis of the partial and local density of states (PDOS and TDOS). In case of O and F as adsorbed atoms, graphene sheets show a wide energy band-gap and some significant magnetic moments. The optical properties of the studied sheets are performed in different radiation regions using the real and imaginary parts of the dielectric function. We think that the energetic, electronic, optical and magnetic properties of the M-graphene sheets are governed by two main factors; the number of unpaired valence electrons and the electronegativity of the M atom.

Ab Initio Investigation of Structural, Electronic, Magnetic and Mechanical Properties of Fe2NiAl1−xGax New Heusler Alloys

SPIN ◽  
2020 ◽  
Vol 10 (03) ◽  
pp. 2050019
Author(s):  
A. Benkaddour ◽  
O. Cheref ◽  
N. Benkhettou ◽  
N. Mehtougui ◽  
D. Rached ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Ab Initio ◽  
Magnetic Moments ◽  
Heusler Alloys ◽  
Plane Waves ◽  
Full Potential ◽  
Generalized Gradient ◽  
Metallic Behavior ◽  
Parameter Values ◽  
Good Agreement

This work presents ab initio study of the structural, electronic, magnetic and mechanical properties of Fe2NiAl[Formula: see text]Gax Heusler compounds with variable concentrations ([Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text]) of Ga. Calculations have performed using the full-potential linearized augmented plane waves (FP-LAPW) method within generalized gradient approximation Perdew–Burke–Ernzerhof (GGA-PBE) formalism in order to describe the exchange–correlation potential. The obtained results showed that the equilibrium parameter values are in good agreement with the available experimental results. In the study of the electronic properties, band structure analysis indicated that all of our compounds have metallic behavior. The calculated total magnetic moments of our Heusler alloys are in line with the Slater–Pauling rule, and they agreed with the results of previous studies. 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 and dynamically stable.

Ab initio band theory approach to electron energy loss near edge structures

1988 ◽  
Vol 46 ◽  
pp. 506-507
Author(s):  
Xudong Weng ◽  
O.F. Sankey ◽  
Peter Rez
Keyword(s):  
Ab Initio ◽  
Local Density ◽  
Interpolation Method ◽  
Atomic Orbital ◽  
Plane Waves ◽  
Large Set ◽  
Theory Approach ◽  
Band Theory ◽  
Atomic Orbitals ◽  
Pseudopotential Calculations

Single electron band structure techniques have been applied successfully to the interpretation of the near edge structures of metals and other materials. Among various band theories, the linear combination of atomic orbital (LCAO) method is especially simple and interpretable. The commonly used empirical LCAO method is mainly an interpolation method, where the energies and wave functions of atomic orbitals are adjusted in order to fit experimental or more accurately determined electron states. To achieve better accuracy, the size of calculation has to be expanded, for example, to include excited states and more-distant-neighboring atoms. This tends to sacrifice the simplicity and interpretability of the method.In this paper. we adopt an ab initio scheme which incorporates the conceptual advantage of the LCAO method with the accuracy of ab initio pseudopotential calculations. The so called pscudo-atomic-orbitals (PAO's), computed from a free atom within the local-density approximation and the pseudopotential approximation, are used as the basis of expansion, replacing the usually very large set of plane waves in the conventional pseudopotential method. These PAO's however, do not consist of a rigorously complete set of orthonormal states.

Effect of Chromium and Vanadium on Nanolayered Ternary Carbides: AB Initio Study

2009 ◽  
Vol 609 ◽  
pp. 239-242
Author(s):  
A.E. Merad ◽  
M.B. Kanoun
Keyword(s):  
Electronic Structure ◽  
Total Energy ◽  
Ab Initio ◽  
Structural Parameters ◽  
Ab Initio Study ◽  
Generalized Gradient ◽  
Generalized Gradient Approximation ◽  
Full Relaxation ◽  
Relaxation Procedure ◽  
Ternary Carbides

The Cr2AlC and V2AlC nanolayered ternary carbides are studied by performing APW-lo ab initio total energy calculations within the recent Wu-Cohen generalized gradient approximation GGA. Using full relaxation procedure of the volume and the atomic positions we obtained the structural parameters and electronic structure of the optimization hexagonal. Results were compared with the experimental ones. Interesting features are deduced. In fact, we have shown why these materials are conductors.

Electronic Structure Of (AgSb)xPbn-2xTen

2003 ◽  
Vol 793 ◽  
Author(s):  
Daniel I Bilc ◽  
S.D. Mahanti ◽  
M.G. Kanatzidis
Keyword(s):  
Electronic Structure ◽  
Ab Initio ◽  
Density Functional ◽  
Full Potential ◽  
Generalized Gradient ◽  
Two Component System ◽  
Functional Theory ◽  
Covalent Interaction ◽  
Salt Structure ◽  
Linearized Augmented Plane Wave

ABSTRACTComplex quaternary chalcogenides (AgSb)xPbn-2xTen (0<x<n/2) are thought to be narrow band-gap semiconductors which are very good candidates for room and high temperature thermoelectric applications. These systems form in the rock-salt structure similar to the well known two component system PbTe (x=0). In these systems Ag and Sb occupy Pb sites randomly although there is some evidence of short-range order. To gain insights into the electronic structure of these compounds, we have performed electronic structure calculations in AgSbTe2 (x=n/2). These calculations were carried out within ab initio density functional theory (DFT) using full potential linearized augmented plane wave (LAPW) method. The generalized gradient approximation (GGA) was used to treat the exchange and correlation potential. Spinorbit interaction (SOI) was incorporated using a second variational procedure. Since it is difficult to treat disorder in ab initio calculations, we have used several ordered structures for AgSbTe2. All these structures show semimetallic behavior with a pseudogap near the Fermi energy. Te and Sb p orbitals, which are close in energy, hybridize rather strongly indicating a covalent interaction between Te and Sb atoms.

Electronic structure of cubic BaTbO3 from first-principles pseudopotential calculations

2006 ◽  
Vol 84 (2) ◽  
pp. 115-120 ◽  
Author(s):  
G Y Gao ◽  
K L Yao ◽  
Z L Liu
Keyword(s):  
Electronic Structure ◽  
First Principles ◽  
Density Functional ◽  
First Principles Calculations ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Exchange Correlation ◽  
Pseudopotential Calculations ◽  
Correlation Potential ◽  
Density Contour

First-principles calculations of the electronic structure are performed for cubic BaTbO3 using the plane-wave pseudopotential method within the framework of density functional theory and using the generalized gradient approximation for the exchange-correlation potential. Our calculations show that cubic BaTbO3 is metallic, and that this metallic character is mainly governed by the Tb 4f electrons and the hybridization between the Tb 5d and O 2p states. From the analysis of the density of states, band structure, and charge density contour, we find that the chemical bonding between Tb and O is covalent while that between Ba and TbO3 is ionic. PACS Nos.: 71.15.Mb, 71.20.-b

scholarly journals Origin of the Low Magnetic Moment in Fe2AlTi: An Ab Initio Study

Materials ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 1732 ◽  
Author(s):  
Martin Friák ◽  
Anton Slávik ◽  
Ivana Miháliková ◽  
David Holec ◽  
Monika Všianská ◽  
...  
Keyword(s):  
Ab Initio ◽  
Magnetic Moment ◽  
Energy Surface ◽  
Magnetic Moments ◽  
Local Magnetic Moment ◽  
Spin Configuration ◽  
Spin Effects ◽  
Order Of Magnitude ◽  
Huge Impact ◽  
Insight Into

The intermetallic compound Fe 2 AlTi (alternatively Fe 2 TiAl) is an important phase in the ternary Fe-Al-Ti phase diagram. Previous theoretical studies showed a large discrepancy of approximately an order of magnitude between the ab initio computed magnetic moments and the experimentally measured ones. To unravel the source of this discrepancy, we analyze how various mechanisms present in realistic materials such as residual strain effects or deviations from stoichiometry affect magnetism. Since in spin-unconstrained calculations the system always evolves to the spin configuration which represents a local or global minimum in the total energy surface, finite temperature spin effects are not well described. We therefore turn the investigation around and use constrained spin calculations, fixing the global magnetic moment. This approach provides direct insight into local and global energy minima (reflecting metastable and stable spin phases) as well as the curvature of the energy surface, which correlates with the magnetic entropy and thus the magnetic configuration space accessible at finite temperatures. Based on this approach, we show that deviations from stoichiometry have a huge impact on the local magnetic moment and can explain the experimentally observed low magnetic moments.

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