Electronic Structure and Atomic Configuration of Extended Defects in Metals by First-Principles and Semiempirical TB-LMTO Methods

1997 ◽  
Vol 491 ◽  
Author(s):  
M. Šob ◽  
I. Turek ◽  
V. Vitek
Keyword(s):  
Electronic Structure ◽  
First Principles ◽  
Magnetic Moments ◽  
Tight Binding ◽  
Local Environment ◽  
Ground State Structure ◽  
Full Potential ◽  
Extended Defects ◽  
Semiempirical Approach ◽  
Sphere Approximation

ABSTRACTWe present two tight-binding linear muffin-tin orbitals (TB-LMTO) techniques for electronic structure calculations of extended defects (such as grain boundaries, interphase interfaces, surface layers etc.) in metals. The first is based on the first-principles self-consistent surface Green's function approach within the atomic-sphere approximation (ASA) utilizing two-dimensional periodicity in the layers parallel to the interface. In the second approach the Hamiltonian is constructed within the TB-LMTO-ASA as well, but semiempirical terms are employed to characterize the repulsive part of the interaction and the effect of electrons in interstitial space. While the adjustable parameters have only been fitted to the properties of ideal ground state structure, the semiempirical approach describes correctly the structural energy differences, phonon frequencies etc. Two examples are presented: the electronic structure of the Σ = 5(210)/[001] tilt grain boundary in tungsten is determined and the sensitivity of 4d magnetic moments in thin films to local environment is discussed. A comparison of the semiempirical TB-LMTO-ASA with the first-principles full-potential LMTO results is performed along the trigonal deformation path connecting the bcc, simple cubic and fee structures and the applicability of the semiempirical approach for simulating atomic structure of extended defects is assessed.

First-Principles Investigation of the Electronic Structure and Magnetic Properties for Co-Doped Fe3O4

2010 ◽  
Vol 654-656 ◽  
pp. 1678-1681
Author(s):  
Yu Hua Hou ◽  
Yu Jun Zhao ◽  
De Chang Zeng ◽  
Zhong Wu Liu ◽  
Li Shi Wen
Keyword(s):  
Magnetic Properties ◽  
Electronic Structure ◽  
Ground State ◽  
First Principles ◽  
Magnetic Moments ◽  
Ground State Structure ◽  
Site Preference ◽  
Generalized Gradient ◽  
Cobalt Ferrites ◽  
Strong Coulomb

The electronic structure and magnetic properties of the (Co1-xFex)Tet(CoxFe2-x)OctO4 spinels (x is defined as the degree of inversion) scenario are investigated theoretically from first-principles, using generalized gradient approximation (GGA) method for the systems with strong coulomb correlations, which gives a correct description of the electronic structure. The GGA+U method gives an improved qualitative result compared with the GGA not only for the excited-state properties such as energy gaps but also for the ground-state properties such as magnetic moments and crystal parameters. The nominal valence of the transition metal elements and the ground state structure have been established based on the study of variation of the cation distribution (x=0.0, 0.25, 0.5, 0.75 and 1.0) over the tetrahedral and octahedral sites. The site-preference calculation on bulk systems indicates that Co2+ ions strongly prefer the octahedral B sites, and the electronic structure and magnetic properties of cobalt ferrites highly depend on the cation distributions even though the chemical composition of the compound does not change. The results are in good agreement with the available experimental data and most of the other theoretical results.

Magnetic Properties of Embedded Rh Clusters in Ni Matrix

1995 ◽  
Vol 384 ◽  
Author(s):  
Zhi-Qiang Li ◽  
Yuichi Hashi ◽  
Jing-Zhi Yu ◽  
Kaoru Ohno ◽  
Yoshiyuki Kawazoe
Keyword(s):  
Magnetic Properties ◽  
Electronic Structure ◽  
First Principles ◽  
Density Functional ◽  
Local Density ◽  
Magnetic Moments ◽  
Functional Formalism ◽  
Rhodium Clusters ◽  
Spin Polarized ◽  
Local Density Functional

ABSTRACTThe electronic structure and magnetic properties of rhodium clusters with sizes of 1 - 43 atoms embedded in the nickel host are studied by the first-principles spin-polarized calculations within the local density functional formalism. Single Rh atom in Ni matrix is found to have magnetic moment of 0.45μB. Rh13 and Rhl 9 clusters in Ni matrix have lower magnetic moments compared with the free ones. The most interesting finding is tha.t Rh43 cluster, which is bulk-like nonmagnetic in vacuum, becomes ferromagnetic when embedded in the nickel host.

First principles calculations of intersite disorder influence on the electronic structure and X-ray magnetic circular dichroism in CoFeMnSi Heusler alloy

2020 ◽  
Vol 31 (08) ◽  
pp. 2050109
Author(s):  
S. Uba ◽  
A. Bonda ◽  
L. Uba ◽  
L. V. Bekenov ◽  
V. N. Antonov
Keyword(s):  
Electronic Structure ◽  
Circular Dichroism ◽  
First Principles ◽  
Heusler Alloy ◽  
Magnetic Circular Dichroism ◽  
Magnetic Moments ◽  
X Ray ◽  
The Rich ◽  
X Ray Absorption ◽  
Circular Dichroïsm

Electronic structure, X-ray absorption, and magnetic circular dichroism (XMCD) spectra in the CoFeMnSi Heusler alloy were studied from first principles. Fully relativistic Dirac linear muffin-tin orbital band structure method was implemented with various exchange–correlation functionals tested. The supercell approach was used to study the influence of intersite disorder, at the levels of 6.25%, 12.5%, and 25% within transition metal sites, on the XMCD spectra at [Formula: see text] edges and spin polarization (SP) at the Fermi level. It is found that most sensitive to Fe–Mn and Co–Fe disorder are XMCD spectra at [Formula: see text] edges of Fe, while the sensitivity decreases from Mn to Co. It is shown that magnetic moments estimated with the use of magneto-optical (MO) sum rules agree with the ab initio calculated ones to within [Formula: see text], [Formula: see text], and [Formula: see text], for Co, Fe, and Mn, respectively. The calculated SP decreases from 99% for ordered CoFeMnSi alloy, to 96% upon 25% Co–Fe disorder, to 83% for Fe–Mn disorder, and to 42% in the case of Co–Mn disorder. The calculated spectra agree well with the available experimental data. The rich XMCD spectral structures are predicted from first principles at Fe, Co, Mn and Si [Formula: see text] edges.

Bond-Order Potentials for Molybdenum and Niobium: An Assessment of Their Quality

1998 ◽  
Vol 538 ◽  
Author(s):  
M. Mrovec ◽  
V. Vitek ◽  
D. Nguyen-Manh ◽  
D. G. Pettifor ◽  
L. G. Wang ◽  
...  
Keyword(s):  
Bond Order ◽  
Tight Binding ◽  
Direct Calculation ◽  
Real Space ◽  
Central Force ◽  
Full Potential ◽  
Extended Defects ◽  
Many Body ◽  
Deformation Path ◽  
Bond Order Potentials

AbstractThe bond-order potentials (BOP) have been constructed for Mo and Nb. These potentials are based on the real-space parametrized tight-binding method in which diagonalization of the Hamiltonian is avoided by direct calculation of the bond-order. In this scheme the energy consists of three parts: The bond part that comprises contributions of d electrons and introduces into the scheme the covalent character of bonding, the central-force many-body part that reflects the environmental dependence of sp overlap repulsion and a pair-wise contribution. The potentials were tested by calculation of energy differences between the bcc and several alternate structures and by investigating the trigonal deformation path. These calculations have been made in parallel using BOP and the full-potential linearized augmented plane-wave method. The central-force many-body Finnis-Sinclair type potentials have also been included into the study of the deformation path. This evaluation of BOP reveals that the potentials reproduce very closely the ab initio results and are, therefore, very suitable for atomistic studies of extended defects in the transition metals.

scholarly journals First Principles Study of Electronic Structure and Magnetic Properties of TMH (TM = Cr, Mn, Fe, Co)

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
S. Kanagaprabha ◽  
R. Rajeswarapalanichamy ◽  
K. Iyakutti
Keyword(s):  
Phase Transition ◽  
Magnetic Properties ◽  
Electronic Structure ◽  
First Principles ◽  
Local Density ◽  
Hexagonal Phase ◽  
Structural Phase ◽  
Tight Binding ◽  
Transition Metal Hydrides ◽  
Lmto Method

First principles calculations are performed using a tight-binding linear muffin-tin orbital (TB-LMTO) method with local density approximation (LDA) and atomic sphere approximation (ASA) to understand the electronic properties of transition metal hydrides (TMH) (TM = Cr, Mn, Fe, Co). The structural property, electronic structure, and magnetic properties are investigated. A pressure induced structural phase transition from cubic to hexagonal phase is predicted at the pressures of 50 GPa for CrH and 23 GPa for CoH. Also, magnetic phase transition is observed in FeH and CoH at the pressures of 10 GPa and 180 GPa, respectively.

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

2016 ◽  
Vol 30 (04) ◽  
pp. 1650028 ◽  
Author(s):  
Sandeep Chettri ◽  
D. P. Rai ◽  
A. Shankar ◽  
M. P. Ghimire ◽  
R. Khenata ◽  
...  
Keyword(s):  
Band Gap ◽  
First Principles ◽  
Magnetic Moments ◽  
Full Potential ◽  
Generalized Gradient ◽  
In Doping ◽  
Spin Polarized ◽  
Band Gap Narrowing ◽  
Linearized Augmented Plane Wave ◽  
Band Gap Tuning

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.

Electronic Structure and Energetics of LaNi5, α-La2Ni10H and β-La2Ni10H14

1998 ◽  
Vol 513 ◽  
Author(s):  
H. Nakamura ◽  
D. Nguyen-Manh ◽  
D. G. Pettifor
Keyword(s):  
Electronic Structure ◽  
Total Energy ◽  
Charge Density ◽  
Tight Binding ◽  
Site Occupancy ◽  
Heat Of Formation ◽  
Hydrogen Atoms ◽  
Atomic Sphere ◽  
Sphere Approximation ◽  
Atomic Sphere Approximation

ABSTRACTThe electronic structure and energetics of LaNi5, its hydrogen solution (α-La2Ni10H) and its hydride (β-La2Ni10H14) were investigated by means of the tight-binding linear muffin-tin orbitals method within the atomic sphere approximation (TB-LMTO-ASA). Preferred site occupancy by the absorbed hydrogen atoms was investigated in terms of the charge density of the interstitial sites and the total energy, both of which indicate that the 6m site in the P6/mmm symmetry is the most preferred. A negative heat of formation of La2Ni10H14 was obtained from the total energy calculations.

Electronic Structure, Pressure Dependence and Optical Properties of FeS2

1997 ◽  
Vol 491 ◽  
Author(s):  
D. Nguyen-Manh ◽  
D. G. Pettifor ◽  
H. M. Sithole ◽  
P. E. Ngoepe ◽  
C. Arcangeli ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Tight Binding ◽  
Structure Study ◽  
Dramatic Improvement ◽  
Full Potential ◽  
Iron Pyrite ◽  
Energy Band Gap ◽  
Equilibrium Lattice Constant ◽  
Observed Behaviour ◽  
Efficient Packing

ABSTRACTA revisited electronic structure study of iron pyrite, FeS2, has been performed using a new Tight-Binding Linear Muffin-Tin Orbital (TB-LMTO) technique in which the radii of overlapping MT spheres are determined from a full potential construction. The interstitial spheres were chosen to provide an efficient packing of space while ensuring that the overlap between the spheres remain small. We have found that this treatment of interstitial spheres results in a dramatic improvement in the description of the electronic structure and the binding energy curves for FeS2 in comparison with a previous LMTO calculation. In particular, the energy band gap, the equilibrium lattice constant and the bulk modulus are all in much better agreement with experimental observations. Moreover, the calculated equation of state is in excellent accord with recent measured P- V data up to pressures of 15GPa with overall deviations of less than 10%. The predicted reflectivity spectrum of FeS2 as a function of pressure gives the observed behaviour of the optical edge. The bonding behaviour the orthorhombic marcasite phase of FeS2 is also discussed within this new TB-LMTO formalism.

FIRST-PRINCIPLES STUDY OF THE EFFECTS OF THE OXYGEN VACANCY ON ELECTRONIC STRUCTURE AND FERROMAGNETISM OF Sn2 Co2O8-δ

2010 ◽  
Vol 24 (14) ◽  
pp. 2229-2235
Author(s):  
KAIHUA HE ◽  
GUANG ZHENG ◽  
HANLIE HONG ◽  
MIAO WAN ◽  
GUANGFU JI
Keyword(s):  
Electronic Structure ◽  
Oxygen Vacancy ◽  
Magnetic Moment ◽  
First Principles ◽  
Magnetic Moments ◽  
Generalized Gradient ◽  
Spin Magnetic Moment ◽  
Metallic Behavior ◽  
Half Metallic ◽  
Single Oxygen

The electronic structure and ferromagnetism of Sn 2 Co 2 O 8 and Sn 2 Co 2 O 7 have been investigated based on the first-principles plane-wave pseudopotential method within the generalized gradient approximation. The calculated results reveal that the oxygen vacancy plays an important role in the electronic structure and ferromagnetism. The Sn 2 Co 2 O 8 shows half-metallic behavior, but by introducing single oxygen vacancy, the half-metallic transits to metallic behavior. At the same time, the spin magnetic moment of every Co atom and the total magnetic moment change greatly. For Sn 2 Co 2 O 8 and Sn 2 Co 2 O 7, the total spin magnetic moments are 1.99 and 3.49 uB, respectively.

Tight-Binding Study of the Electronic Structure of the high Temperature Superconductor La2CuO4

1987 ◽  
Vol 99 ◽  
Author(s):  
D. A. Papaconstantopoulos ◽  
M. J. Deweert ◽  
W. E. Pickett
Keyword(s):  
Electronic Structure ◽  
High Temperature ◽  
Band Structure ◽  
Fermi Surface ◽  
First Principles ◽  
High Temperature Superconductor ◽  
Tight Binding ◽  
Binding Study ◽  
Three Components

ABSTRACTWe have fit our first principles LAPW band structure results for the high Tc superconductor La2CuO4 to a tight-binding Hamiltonian that contains s, p, and d interactions from the three components of these materials. Our fit reproduces very accurately the 17 lower bands of this material and especially the Fermi surface.

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